There were no formalities when we reached a gunboat attached to one of the El Salvadorian Navy ‘Reaction Force’ flotillas. The blue and white flag on the mast bore the words Dios, Union y Libertad across its broad, white horizontal stripe.

Within minutes we were heading out towards the far side of the gulf. The shores facing us, said the youthful captain, Byron Roberto-Rivas Alfonso Pinto, were Nicaraguan. Having passed round his card, as protocol demanded, he suggested that we call him Captain Bob. With Brown and MacKenzie, we now had three Bobs onboard.

The 110ft naval patrol boat was immaculate. The crew probably knew we were coming and had prepared accordingly. There were two .50-cal Browning machine-guns, mounted fore and aft, and the weapons were well greased. There were more automatic weapons mounted alongside the bridge. Aft, strapped down, was a 14ft Zodiac. It performed a double function: as a lifeboat and for use in shallow inshore patrols among the mangroves. The crew was dressed in camouflage, with nothing to distinguish sailors from soldiers; no formal whites anywhere. Best of all, the heads down below had been scrubbed.

Life on board consisted almost solely of patrolling a fixed area out to sea. They would intercept and stop small boats and fishing smacks that crossed the bay, which, at its widest was about 30 miles across. These craft were sometimes searched for weapons and illegal entrants and if the crew had a bit of luck, the captain told us, they got themselves an insurgent or three.

‘We can’t search every boat or arrest every suspect. But we know that the other side are using these waters to bring across their people and their weapons. It’s a very active area’, he told us through an interpreter.

‘Sometimes, when we’re sure, we let one or two of the suspects pass to see where they lead us. But that’s a big operation and it can get complicated… it needs lots of men on the ground to follow through. And the enemy is not stupid.’

We were offered breakfast, American style, with bacon and eggs and a gritty grey bean paste instead of hash browns. The coffee was percolated, local and good.

Captain Bob told us of something that had taken place a month before. He’d stopped the same shallow-draught boat for the third time in about as many weeks. It was always in the same area, usually towards sunset. ‘We were even on nodding terms with the crew of two,’ he declared.

This time she had her lines out and somehow, I sensed something wrong. There was nothing I could put my finger on, but I felt it… in my bones… these hombres were up to something. But they were too clever for me. I knew it…

So, the third time I came on them, I did something I hadn’t done before. We had some soft drinks and I offered them some. So they came on board. We talked a little: about the weather, the fishing, the war, even about Nicaragua. And since it was getting late, the taller of the two men, a young fellow with sharp eyes and not much to say, offered me his hand. He had to go, he told me.

They shook hands and the pair turned to go. Then Captain Bob realized that the hand he had grasped was not the callused paw of a fisherman. The palms were soft, the grip flabby. This was no tarry sailor.

‘I had him, I knew. But we had to be careful.’ We steamed on, but not too far away. Meanwhile we inspected several other boats, keeping our suspect in sight. I radioed to headquarters and asked for a helicopter and a couple of marine commandos with diving gear.’ An hour later most of the support team was ready and waiting at La Unión, but the helicopter had to come from San Miguel and that took a little longer.

The fishing-boat didn’t move, but light was now fading and the commander feared that they would lose them since it gets dark quickly in the tropics.

‘The one advantage that we had was that the sea was calm and there was no wind.’ Not long afterwards the familiar roar of the Huey could be heard. It approached from the shore, directly towards them. ‘We told it to lower a winch, and in two minutes I was in the air. Meanwhile the officer of the watch kept the boat in his sights. We made straight for it.’

Still in touch with the naval craft, a lookout said that the two men were hauling in their lines. In another minute they would have made off.

‘We had only seconds to drop a marker. My vessel was following as fast as her 26 knots allowed.’

What happened next is in the record books in San Salvador. The helicopter dropped its marker alongside the boat and the two men, now covered by a twin-barrelled 7.62mm machine-gun, were ordered through a loudhailer to sit tight and await the navy while two frogmen went into the drink.

They found a weapons cache wrapped in double plastic bags that had been attached to the fishing-boat. The two on board had slipped the cable the moment they spotted the inbound chopper. Too late: they hadn’t counted on navy divers. The sea was barely 15 feet deep.

This particular pair had been smuggling weapons into El Salvador from Nicaragua for months. On a previous occasion, when things looked like going off kilter, they’d simply jettisoned their cargo and it sank to the bottom without trace. Never mind: they would go back to Nicaragua and get more. At that time the Sandinistas were getting all the weapons they needed from Cuba.

The manner in which the hardware was being shipped is interesting. Attached to the harness that held the loads, there were two small flotation bags that supported them just below the surface. In a cumbersome manner the ‘fishermen’ were able to tow their loads ashore. If challenged, it was easy to turn over a bag and lose it.

In those calm waters they had enough warning. Visibility was invariably excellent and when your engines weren’t running, you could hear a man talking a mile away.