The following morning, I fully took charge of the loading of kit onto our vehicle, having carefully placed the Sesame Street cake in the back bin and covered it with camouflage and a waterproof protective sheet. Our driver, a lad called Dan, was in on my secret as I didn’t want him to throw a heavy bag in the back bin and squash Big Bird. The squadron leader gave me an awkward wink, looking for reassurance I’d followed his plans to the letter. I gave him a thumbs-up and pointed to the back bin.

Eventually we rolled out of the back gates and onto the vastness of the Canadian prairie. I enjoyed being a passenger rather than the driver, where I would constantly have my ability scrutinised. I’d vowed never to be as ridiculous as some previous gunners I’d had the displeasure of driving for. Some could be unfair and, to be blunt, turn into whinging backseat drivers.

Initially we had a large move to carry out. We were travelling to the extreme north of the area, a trip that would take three hours easily. In the fortnight since we’d last been out, I could feel the temperature had dropped; to me this was a good thing as I’d found the heat overpowering on occasion during the first exercise. As we bobbed along, occasionally banging our hips on the hatches to our turret, Harry and I shared Haribo and the three of us participated in light conversation and banter over the vehicle’s intercom system, which was crucial to communication because of the noise of the diesel engine and constant sound of tracks cutting up the ground.

Harry mentioned that he and his brother had been informed some time ago that they were both gay icons. This caused me to laugh.

‘What? What? We are!’

‘I don’t think you are, sir!’

‘Why? We are! Our press people told us!’

‘Honestly, I’m sure you’re not…’

‘Is it because I’m fucking ginger?’

I could hear Dan giggling. Harry laughed a little and we returned our concentration to the task at hand. After what seemed like an eternity, we finally reached our location.

Almost immediately, the leader spoke with me on the quiet and told me to prepare the cake, shoving a bunch of feeble candles into my hand. I carried the cake in secrecy to the back of a Land Rover. The last thing in the world I needed at that moment, as the entire squadron and our infantry friends grouped together to listen to the leader’s address, was gusting wind but guess what? It seemed windier than it had ever been.

I lit the candles, nervously looking over to the men who were about to sing ‘Happy Birthday’ to the prince. The leader was buying me time by welcoming everyone to the exercise but I could tell he was getting impatient.

Realising I had little choice other than to hope for the best, I shielded the cake and candles from the wind as best I could and made my way into sight of the boys and Prince Harry. On cue, the guys burst into jubilant song.

Upon reaching the prince, who’d been ushered into the centre, I presented his cake, with its extinguished candles, and wished him a happy twenty-fourth birthday. ‘You’ve fucked this up,’ he joked, shaking my hand. It was exactly the right level of humour required at that very moment. The leader led the applause and everyone wished Harry three cheers. Our entertainment was over.

‘Where the hell did you find that cake?’ the leader asked afterwards. I resisted boring him with endless points about the lack of resources available to me considering the time frame I had to work in. In fact, he loved the cake, everybody did. The staff responsible for conducting the exercise told Harry and me that we were the prize target for the training troops, who’d caught wind that Harry was one of the enemies out to get them. They warned us that we would probably be the priority target in every battle throughout the two-week war and that we shouldn’t become too disheartened by the fact.

The enemy had carried out their intel and discovered what call sign our vehicle was. 9.1 had become the main effort for the training troops, but Harry was ready to take on their fight and outsmarted them from the start.

Cleverly, Harry decided to change the numbers on our vehicle with another. The commander of the vehicle in question was quite put out about the whole thing, but Harry held more weight as an officer than the corporal in command of the now doomed vehicle. The decision was made. I’d find this was just one example of the sharp wit and clever tactics I’d remember Harry for.

The exercise got off to a flying start. Between the two of us we had a good tally of confirmed kills and Dan was an excellent getaway driver. We’d taken on some pretty large outfits of men and generally come off the better.

As our time on the prairie progressed, the activities we were asked to undertake gradually became more and more challenging. One night we were given a long move to carry out, under the cover of darkness and in full tactical conditions.

It was a painstakingly long drive, which minute by minute became more stressful for me as a passenger in the turret of our vehicle. I realised that I was a much calmer soldier being responsible for the safe delivery of a crew, in the driver’s seat as opposed to standing by and relying on someone else.

The calm prairie landscape was interrupted occasionally by a sombre lone white cross, signifying the precise spot where a soldier had lost his life in a training incident. I’d have felt more at ease if there was only the odd one of these but, much to my distress, there were many. I considered the sadness a loved one must feel on hearing the news that their soldier had died in a peacetime accident while training in Canada. After the previous year spent abroad in hostility, I know that news would crush my own mother.

Throughout the move, Harry, much to my relief, had decided on occasion that the landscape was too severe and gave the order for Dan to switch on our headlights. As soon as the immediate danger had past, Harry had the lights turned off again, in keeping with our orders.

Dan also had his night-vision sight, used from inside his driver’s cab; Harry was using a night-vision device he’d acquired from somewhere, too. I spent most of the journey hoping for the best with my bare eye.

Suddenly, chaos ensued. We’d been driving along at an incredibly steady speed, a little over ten miles per hour, when out of the complete blue, smash! We’d landed in trouble.

The whole thing happened in an instant. While crawling along, none of us had noticed a sudden drop in our path, completely undetectable in the sheer darkness of the vast Canadian plain. The moment we rolled off the edge of the drop, I thought we were driving off a high cliff, heading for the ground far below and our death. The drop seemed to last forever and as soon as we hit the bottom of the hole we’d driven into, the three of us were knocked and tossed around our small armoured vehicle. I was thrown forward and my head hit the sighting equipment to the main weapon system. I could hear through my headset that Dan was conscious and making a noise. I looked over to Harry, sat just a foot away from me in the centre of the turret, dreading what I’d see.

Like me, he’d been thrown face first into his sights and was rubbing his face after the knock he had just taken. The commander and gunner relationship was quickly forgotten as I grabbed him to make sure he was OK. He was. Although I’d not totally switched off from the fact that he was a high-ranking member of the royal family, he had become familiar enough to me and enough a part of my everyday life to be considered one of the lads.

The three of us climbed out and drew what artificial light we could onto our damned vehicle to survey the damage. The drop, although it had felt severe and long, was actually about two metres. Initially I’d considered the vehicle to be in a desperately poor state, but apart from the crushed stowage bins at the front and a couple of smashed headlights, it looked in good working order.

Throughout the move Danny and his crew had been driving behind us. As soon as we were no longer detectable in front, he’d switched his headlights on. With his wealth of experience, he took charge of the situation and oversaw the recovery of our vehicle.

The accident did nothing for my confidence with regard to being a passenger rather than a driver, and I couldn’t help feeling that the incident had really knocked my courage levels in being a gunner. The ditch we’d driven into could easily have been a cliff or even simply a larger hole, resulting in a much worse outcome. I also felt that Harry had to an extent enjoyed the experience; I think it underlined the dangers associated with armoured vehicle tactics and the realism of training for war, maybe reigniting feelings he’d experienced earlier in the year while fighting in Afghanistan. In the hours that followed, after endless worrying, Harry told me to ‘man the fuck up and stop acting like a fanny’.

Mid-exercise, Harry was called to a briefing along with the other commanders, reviewing the progress of the exercise. When he returned, he looked more than a little excited.

‘Great news, we’re the call sign with the most confirmed kills!’

He was right, this was great news. To be in the running for ‘top gunner’ on my first exercise was pretty incredible.

‘I want to win this title!’ Harry exclaimed.

We had our carrot, and we intended to see the job through. The infantry soldiers, who like us were steeped in tradition and history, were offering a medal to the call sign crowned Top Gun at the end of the exercise. Within their regiment, one of these medals was seen as a very notable achievement. Although fairly insignificant to us Household Cavalrymen, in reality the competitive streak in both Harry and me really whetted our appetite. We wanted that medal.

Our hunting began in earnest the following day. At one point, it was going so well I couldn’t help considering why we were achieving so many ‘confirmed kills’. Was our enemy simply not as good as us or were they just not putting enough effort into their training?

Throughout our trials, there was one recurring point that marred our impressive tally: my fairly inexperienced drills in turret. Yes, I was getting the kills, but carrying out the correct drills in order for me to get a shot off onto the enemy was continually going wrong. The news that another call sign in our enemy collective was catching up fast with us only fuelled tensions in our turret.

Harry had tapped into a member of the exercise staff who was feeding him information on how many kills we were on and how many our closest contender was on too. He’d hear daily if we were in a comfortable lead or if things weren’t looking great.

Three days before the end, the gap between us and the other call sign, manned by soldiers from the Royal Tank Regiment, was down to just two. All our hard work had been closely matched and we worried the chance of winning Top Gun was slipping away from us.

Patrolling along in an area where we knew the enemy was hiding, suddenly we encountered a fully exposed main battle tank sat broadside on the top of a hill. It was a dream of a target for me, as all I really needed to do was aim into the centre and fire. I was in position quickly and when Harry gave the order to fire, much to his and my annoyance, nothing happened. Immediately I knew I’d made the same mistake again, only this time things really mattered as we desperately needed to improve our kill tally. By the time I’d sorted the problem and pressed the button I was continuously forgetting to press, the tank had driven off and into cover. A missed opportunity.

Annoyed, Harry turned to me. I knew I was in for an ear bashing.

‘If you forget to do that again, I’m seriously going to knock you the fuck out!’ He wasn’t joking.

I could hear Dan cough uncomfortably in his driver’s seat. Harry was understandably frustrated. It was my responsibility to carry out the drills properly in order to successfully destroy the enemy without hindrance. I’d failed and he was furious.

For about an hour hardly a word was spoken and, as if our day couldn’t get any worse, somebody managed to get a shot off on us which took us out of the battle. We’d hopelessly managed to add nothing to our kill count, and we fretted thinking about how many kills the other team was getting in our absence.

We remained at the location we’d been destroyed at for about six hours, mock battles still raging around us. We displayed our shamed green flag, signifying our redundancy from the game.

Dan was becoming chattier as the exercise continued. At first, I think he was quiet due to the situation he found himself in. Among the squadron, apart from Scoffy, I was probably the loudest character. The added weight of having Lieutenant Wales meant that he just didn’t seem to make much noise. It was good to get to know him.

Harry took the opportunity of being alone in the middle of nowhere with the two of us to have a bit of a chat. Thankfully, he seemed to have forgotten about the whole gunnery incident and the three of us passed the time by discussing each other’s backgrounds.

Harry asked what our plans were for Christmas and in turn we both told him. The hours passed by nicely and I realised how very surreal and rare an opportunity it was to hold a personal discussion with one of the most famous men in the world.

‘When did you realise you were gay?’

‘I always knew to be honest. Just never really wanted to say.’ Harry nodded in understanding. Dan piped up with another question.

‘Have you ever had a girlfriend, like?’

‘Yeah… I had one when I was growing up, nothing too serious though.’ I thought that might have been the end of the conversation.

‘Did you ever sleep with her?’ asked Harry.

‘I did, actually. I don’t think I was ever any good at it though. I certainly didn’t enjoy it.’ The three of us laughed at the thought.

‘How old were you?’ asked Harry.

‘About fifteen. It was more about keeping face.’

Dan then explained the circumstances surrounding the loss of his virginity, captivating both Harry and me.

‘Well, you’ve heard ours,’ I said, turning to Harry. ‘What about you? When did you pop your cherry?’

Harry told us both an extraordinary tale about what exactly happened in the lead-up to the first time he’d had sex. It was fascinating. Afterwards, I considered what diverse backgrounds the three of us had, but how we’d all completely accepted the differences in our lives and shared our stories. Dan’s was interesting because of the environment he was raised in; mine was different as it involved both boys and girls, and Harry’s was unique simply because he was born into the royal family. Class went out of the window, as did upbringing and sexuality. While we shared our personal stories, the three of us leaned on an unspoken pillar of respect that bonded us as a team. It was incredible.

The exercise team resurrected our vehicle overnight and at six the following morning we were ready to embark on our penultimate day of hunting. We had no idea if we still held the lead on the kill front, but we desperately wanted to take the crown upon the call of ‘end-ex’ the following day. The usual excitement surrounding ‘end-ex’ was fairly insignificant to me on this occasion; I knew it would mark the end of mine and Harry’s time working together.

The day started off well. I’d consciously made an effort to rid myself of my repeated mistake behind the gun. Our enemy were as professional as they’d been throughout – so, not very – and we tallied our way through the morning.

After one such battle, Harry decided we could have a break and I dropped into the turret to make the three of us coffee, using the boiling vessel stored inconveniently in the corner. Harry’s thermal mug was bright orange and I joked that it matched his hair.

Over the radio, while enjoying the lull in activity, the three of us heard a call for help. Harry answered, stating our position. The call was for medical assistance after a crash of some sort.

‘They need a medic!’

‘I’m a team medic if that’s any help?’ I returned.

A team medic was a soldier who wasn’t a professional medic but trained as much as possible to step up into the medic role if the situation ever called for it. They were introduced for the Iraq and Afghanistan conflicts as a way to deal with the endless streams of casualties and the fairly small number of ‘proper’ medics on hand at the time.

‘I’ve got a team medic here, we’re 2 km away from you,’ Harry told the worried person over the radio.

Suddenly we had our green flag flying and were on our way to help somebody. The pair of us mentioned that it was far from what we’d have wanted, but ultimately the right thing to do. We got to the stricken vehicle and spent about thirty minutes with them, giving what immediate care I could. Soon enough a safety vehicle came and took the injured guy, and his crew, away.

The day was over not so long after. The battle had purposely ended early to give everyone the chance to rest ahead of the final push. Harry had been briefed and found that we were completely level pegging with the Tank Regiment call sign and the competition for Top Gun was going to run right to the end.

The vehicle in question, our nemesis in the running for the Top Gun award, parked right up next to us that night. It was a nice opportunity to talk with the guys from the Royal Tank Regiment. They teased that we might as well forget about winning the prize and we returned with, as expected, like-for-like comment. I had somewhat forgotten about the status of our crew with our very special commander, but seeing the jubilant faces on the visiting Royal Tank Regiment crew’s faces, at once I was aware of our situation again. I wondered if Harry knew how important and proud a moment it was for people to see him and serve with him? Harry’s – and William’s – story was one the whole nation had been caught up in. Every single person in the country had a vested interest in their livelihood. We’d all seen them grow up on our screens, in our papers, and to suddenly be thrown into the middle of that whirlwind of a life was simply remarkable.

Our final day started early. We were to lie in ambush awaiting the passing of the enemy troops. They appeared right on time and we opened up on them, claiming an easy three kills in the process. We dampened our own celebrations, knowing that our rival call sign would have probably had the same success from their vantage point. A little after our ambush we carried on the hunting game and took out another two vehicles. I imagined the pride of marching out and collecting our medal. It was my first time in the turret and I might be awarded from the start.

Out of absolutely nowhere, our sirens started to sound and our lights began to flash. We’d been hit. I dropped down into the turret to read the display screen. We’d been destroyed. Our fight was over. I stood back up and saw Harry swearing at someone. A sneaky enemy Challenger Two tank had crept up on us from behind a hill. It took one shot. Our running for Top Gun was over. We were in the hands of the gods as far as victory was concerned.

In an incredible turn of events, our rival vehicle drove straight into our area and entered a battle with a group of infantry soldiers who were heavily armed with anti-tank weapons. The three of us sat on our doomed vehicle and watched as they drove right into the path of the waiting troops. In a flash, they’d been destroyed.

From the distance we could see their commander throw his headset off. He was having a right go at his gunner, who just stood there looking sheepish. Harry and I laughed. They reversed and pulled up next to us.

‘How many kills did you get?’ the young commander shouted over. I was about to reply with the truth, but Harry beat me to it.

‘About twelve!’ The face on the commander dropped. They drove off and settled in the spot they’d been destroyed in. Defeated, the commander displayed his green flag.

‘I’m not letting on to those cunts!’ Harry said afterwards, a grin on his face.

Shortly after, the ‘good guys’ had defeated all of us ‘baddies’. The war was over. End-ex!

We had a long journey back to Suffield, which took about two hours. Nobody spoke about the result; we were left brewing for the entire journey. Upon finally reaching our hangar, Harry dashed away to sniff out a potential result, leaving Dan and me to unpack our kit and put the vehicle to bed. He returned some time later, expressionless.

‘Well… Did you learn anything?’

‘WE GOT IT!’

The three of us jumped up and down with joy. It was like winning the FA Cup. I couldn’t believe it. Trooper Wharton: Top Gun at the first attempt. I put it down to the winning combination of a prince and a commoner from North Wales.

Danny and Scoffy were both chuffed for us. Danny bought lots of drinks at the bar that night and referred to me as ‘Top Gun’ constantly. I was over the moon.

The following day, the entire group of enemy troops was pulled together. The colonel from the infantry regiment wanted to say a few words about the exercise and, of course, present me with my Top Gun award. I was extra smart that day and walked with a spring in my step.

All 200 of us formed up. Harry, Dan and I stood together, so the three of us could lap up praise when the right moment came. The colonel began with the usual spiel about effort and congratulated us all for performing well throughout. Then it was on to the prize.

‘The crew with the most kills has performed far better than anyone ever expected. They showed grit and determination throughout.’ I was struggling to keep the smug grin off my face. ‘So I’d like the commander of 9.1 to come out and collect this award, Lieutenant Wales!’

Harry sprang to attention and marched out. I couldn’t believe he was being rewarded for my skill behind the gun. Where was the justice? He accepted the award and the entire enemy force applauded. No award for me!

Afterwards, the squadron leader came to congratulate me and patted me on the back. I thanked him but moaned that I’d not received a medal, to which he laughed. ‘That’s how it works, Trooper Wharton. The commander always takes the glory.’

And he was right. It was, of course, Harry’s strong leadership – far stronger than most of the officers I’d ever worked with before – that had got us to the level we were at. From his relatively short experience, I’d learned a hell of a lot about commanding. He’d shown me how to navigate best with a GPS, how to ‘sneak’ around hillsides and land features without exposing the vehicle and, more than anything, he’d shown me how to command with real leadership. Without his motivation and attributes as a boss, undoubtedly we’d not have achieved the Top Gun status we had.

I knew that Lieutenant Wales wasn’t staying with us for our final exercise in Canada, but had to head back to the UK to be a prince again for a while. Throughout our time together in the turret of 9.1, there wasn’t a single moment that I didn’t cherish. I’ll probably never meet him again but I enjoyed every bit of the exercise with him. I appreciated his openness, the way he spoke with personality on almost anything, the way he almost stripped his royal title off himself every time he entered the turret next to me. Most of all, I admired his kindness. I’ll never forget the four weeks we worked together and the incredible conversations we shared. Today, whenever I see him on TV, I want to tell the person next to me that I ‘knew him once’, but every time I do, I stop myself. The four weeks I spent with him were, of course, professional and part of my duty as a soldier. On leaving the service and moving into the civilian world, the experience lives on in my memories as the single most stand-out period of my decade in the military. I will never forget the time I spent with Prince Harry.