Big Ben pulsed like an evil heart as the Raven Banner’s magical energy wrapped around it in a shimmering red haze. At the tower’s base, red cracks ripped open the pavement, radiating out along ancient ley lines like a spider’s web. Soon they would spread the berserker spell across the whole of Britain, waking the blood of every Viking ancestor.

On Westminster Bridge, Declan Appleby, a mild-mannered bus driver from Catford, transformed into a Viking berserker and deliberately crashed his open-topped bus into the back of a taxi. The bald-headed taxi driver got out of his car, up for a good old-fashioned London road-rage argument. That was until he saw Declan’s bulging muscles, foaming mouth and burning red eyes.

In her Lambeth primary school, Sarah Axelsen was teaching fractions to Year Four when she suddenly went full berserker as the spell hit, let out a roar, kicked her desk over and jumped through a window. Her class sat in stunned silence, until two of their classmates also transformed, bellowing Old Norse oaths as they ripped their maths textbooks to shreds with their sharp, yellow teeth.

Everywhere the red cracks in the earth appeared, someone turned into one of the Viking monsters. Berserker chefs abandoned their kitchens, but not before noisily feasting on the raw meat they were preparing. Metamorphosed plumbers smashed toilets and sinks, screaming in rage. Transformed traffic wardens tipped over the cars they were giving tickets to moments earlier. London was fast finding itself in the grip of berserker mayhem.

At Ten, Downing Street, Prime Minister Thorn, still recovering from her encounter with the Defender and Qilin, found herself hauled from her office by two security agents.

“Ma’am, there is an emergency. We have to get you to the safe room.”

As they ran her along the corridor and down the stairs, Thorn caught a glimpse of the chaos outside. A bus was on fire and what looked like a crazed giant in a ripped policeman’s uniform was tearing up paving slabs with his bare hands.

“What’s happening?” she shrieked as they reached the basement.

“We’ll brief you inside COBRA, ma’am,” said the agent as they pushed confused staffers aside and stampeded through.

COBRA stood for “Cabinet Office Briefing Room A”, which didn’t sound very exciting, but it was the specially equipped room from which the prime minister could deal with any crisis, even a war. Thorn knew that if they were going there, then this was serious. Behind them a crack ripped through the floor, carrying its glowing red magical payload. They reached a heavy metal door. One of the agents keyed in a code and opened it. Ignoring the screams and yells coming from the rest of the building, the agents pushed the prime minister inside, followed her in and secured the door.

The COBRA room contained a long desk and a bank of screens that were already being monitored by those senior military figures lucky to be have been close enough to Downing Street when the disaster began. Here, in the secure bunker, they were completely safe. The senior agent wiped the sweat from his brow and spoke into his radio.

“The prime minister is secure. Repeat, the prime minister is…”

A low growl filled the room. Everyone looked around for the source of the noise. The prime minister was hunched over the desk, her body shaking with violent jerks. As the assembled staff watched in horror, her shoulders burst through her suit, her hair turned blonde, growing thick and long, and her face became purple with Norse tattoos. She roared and punched the desk in half with a mighty, gnarled fist, as the agents scrambled too late for their guns.

At Wimbledon, Kate Robertson was about to serve for the title. A few people in the crowd had suddenly become engrossed in something on their phones and a couple had even left, but most were still enthralled by the game. A chorus of “Come on, Kate!” echoed around the arena.

“Quiet please!” said the umpire.

In the royal box, Ellie leaned forward, excited, while Alfie kept a concerned eye on the darkening sky. Was that thunder he heard rumbling in the distance?

“Alfie, just watch,” Ellie hissed. “This is going to be historic.”

Kate Robertson bounced the ball patiently and waited for complete silence. She tossed it high in the air to serve. Around the country, several million pairs of eyes watched the ball reach the top of its trajectory and fall back to Robertson’s waiting racquet. WHACK! She sent the ball high over the net … and clean out of the arena! The crowd’s gasp was as loud as a jumbo jet. Britain’s number-one tennis player had transformed, her berserker face stained with bright blue tattoos, her hair suddenly blonde and bushy. Brandishing her racquet like a club she pounded the ground. With a ripping sound, a glowing red crack appeared in the famous grass as if a knife had been drawn across the court.

“Racquet violation, Miss Robertson!” the umpire yelled.

But no one in the crowd was listening. They were too busy scrambling for the exits away from some of the spectators who, as the magic took hold, were also turning into Viking berserkers, tearing up their seats and throwing their picnics into the air.

“Alfie, what’s going on?” said Ellie, looking to her brother.

But Alfie wasn’t in his seat. He was already disappearing through the exit to the private VIP area behind the royal box. Ellie was aghast – he had deserted her at the first sign of trouble.

“ALFIE!”

What Alfie was really doing was looking for somewhere quiet where he could put on his Defender armour without being seen. Because whatever was happening out there, he knew what this was – this was Lock and his brother and the Vikings – this was their plan. He just hoped it wasn’t too late to stop them.

Meanwhile, a few miles north of London, Hayley had finally reached the Whisper Grove Care Home and burst into her gran’s room.

“Ah, nurse, good, I need some help,” said Gran, not recognizing her as she glanced up from the television she was watching. “The tennis has gone all funny.”

Hayley just clocked a snippet of the panic on Centre Court before the broadcast abruptly ended. She took the brakes off her gran’s wheelchair and helped her into it. Whatever was going down at Wimbledon, she hoped Alfie could handle it. Right now, she needed to get Gran out of here.

“Gran, it’s me. I thought we’d go on a little trip – the countryside, maybe,” said Hayley, as she weaved the wheelchair towards the exit.

She thought she would have trouble getting past the home’s staff, but everyone seemed glued to the TV news.

“That sounds nice, dear,” said Gran, seeming to understand who she was again.

Outside, a strong wind buffeted the trees. A storm was blowing in. Hayley ran quicker, looking for a car she could take.

“What’s the rush, child?” Gran said, gripping the wheelchair’s armrests.

“Just want to beat the traffic, Gran,” Hayley said.

“Can we offer you a lift?” said Agent Turpin, leering as he stepped out from behind a bus stop.

Agent Fulcher appeared and grabbed Hayley, lifting her off the ground. They must have been staking the place out all along.

“Thought we’d given up on you, didn’t ya?” Fulcher shouted, triumphant.

“Get off!” Hayley cried, struggling.

But Fulcher had her in an iron grip. Turpin was holding a pair of handcuffs. They’d obviously learned their lesson since last time.

“Hurry up and cuff her, she’s as slippery as a bag of eels!” Fulcher said as Hayley squirmed.

With an ominous click, the handcuffs locked themselves tight around Hayley’s wrists.

“Hey, you’re the man who wants to stop bingo!” Gran said to Fulcher.

“No, I’m not. And I’m not a man, either,” Fulcher complained.

“DON’T TOUCH HER!” yelled Hayley.

Turpin, smiling like a piranha, helped Gran out of the wheelchair and into the back of their car.

“Now, then, Mrs Hicks. How about that day trip, then? We’ve got a lovely place we can take you while we have a little word with your granddaughter.”

Gran looked doubtful, her eyes clouded. “I want to see Lawrence.”

“Don’t listen to them, Gran!” Hayley shouted, glaring at the agents. She couldn’t believe they would stoop so low as to tease a fragile old woman. “Gran might be sick, but she’s not as sick as you two!”

“You know, I almost hope you resist spilling the beans about who your Defender friend is,” Turpin said. “That way I can let Agent Fulcher do what she does best.”

Fulcher grunted her approval and threw Hayley into the back seat next to her gran.

As the car sped back into the city, Hayley stroked Gran’s hand, comforting her, and plotted her next move. She couldn’t make a run for it and leave Gran with these two thugs. But maybe she could get someone’s attention and scream for help. However, as she scanned the streets for the police, she noticed cars abandoned everywhere and people running around in a panic.

“Something’s happening out there,” she said.

Turpin turned round and sneered. “Nice try. But you’re not getting out of it this time, missy.”

Suddenly the car jumped as a red crack split open the road beneath them. Hayley flung herself in front of her gran as they skidded to a halt. She sat up to see Fulcher with her nose to the window, watching a group of berserkers rampage past, pulling down road signs and terrorizing screaming pedestrians.

“The girl’s right. Something’s wrong, Turpin.”

She looked over to see Turpin’s head touching the roof of the car, his face bulging and wild-eyed, his shoulders and arms expanding till they were bigger than hers.

“RAAAAAAAARGH!” berserker Turpin bellowed, wrenching off the steering wheel and punching it through the windscreen.

Fulcher screamed a surprisingly girly scream and tumbled out of the car.

“WAIT! HELP US!” shouted Hayley.

A cab slammed into the back of them with a crunch, sending their car spinning again. When it came to a rest, the door next to Gran was hanging off its hinges. Relieved to find they were unhurt, Hayley leant against her gran, pushing her out.

“GRAN, WE NEED TO GO!”

Hayley rolled out to see berserker Turpin leap on top of Fulcher, clawing and biting like a rabid dog. Fulcher was punching back, giving as good as she got, but for once they were evenly matched. As they rolled past grappling with each other, Hayley saw the key to the handcuffs fall from Turpin’s torn trousers. “The key!”

“I’ll fetch it, dear,” said Gran breezily, not seeming to grasp how perilous their situation was.

“No, Gran!”

But before Hayley could stop her, Gran had shuffled over, picked up the key and brought it back – just in time as Fulcher staggered past again, carrying a flailing Turpin on her shoulders like he was an unruly toddler.

“GET OFF ME!” pleaded Fulcher.

Gran released the handcuffs and Hayley rubbed her sore wrists. She pulled Gran away from the havoc on the road, looking for somewhere – anywhere – they might be safe from this outbreak of … of whatever it was.

Meanwhile, in the Map Room, LC and Yeoman Box stared, dumbfounded, at the ops table alarm lights. Every single one of them, the length and breadth of the kingdom, was flashing. As the Raven Banner’s magic travelled along the ley lines of Britain, Burgh Keepers were sending in frantic reports of sortilegic meters ringing off the scale. In the Keep, grim-faced Yeoman Warders rushed around, answering the phones and plotting the dark magic’s unstoppable advance.

“The Wandle ley has gone past Wimbledon now, sir!” shouted Brenda.

“Greenwich Burgh Keeper says his meter’s just exploded!” yelled another beefeater.

LC stared at the map in despair. Nowhere was safe from the magical infection. Transformed berserkers would soon be in every city, every county, every village. A ready-made army of lunatics to do Lock’s bidding.

“Ragnarök,” muttered LC, darkly.

“I think I’ve got one of their albums,” said Brenda.

“It means the Viking apocalypse. Chaos. Fear. The end of the world as we know it. We MUST find His Majesty!”

“No word from the Defender!” shouted the beefeater manning the radio link.

The last they’d seen of Alfie he’d been at Wimbledon before the screens went down. The powerful magic sweeping the land must have been interfering with mobile communications, as only the old-fashioned landline telephones seemed to be working.

“What are your orders, Lord Chamberlain?” asked Yeoman Warder Gillam, not quite managing to control the tremble of fear in his voice. “What should we do?”

LC gazed around the Map Room. With Alfie missing, Brian on the run and Hayley also absent, panic was starting to creep in. Even Herne was behaving oddly, turning in circles, barking and whining.

“Keep calm and defend the realm!” LC barked, striding up and down. The beefeaters stopped what they were doing and watched him. “The Tower of London has stood impregnable for nearly a millennium. It has faced down every enemy ever sent against it. The Black Death Rat Men of 1348. The Dragon Storm of 1666. Even Hitler’s Abominable Snow-Nazis could not crack its walls. It shall not fall—”

The Keep shook as a powerful earth tremor struck. Plaster fell from the ceiling and a grand tapestry depicting a past Defender’s victory over the giant bats of Wookey Hole fluttered to the floor. A wide, red crack snaked under the main doors and through the Map Room, sending Yeoman Warders diving for cover and splitting the Tudor Rose on the floor in half. The ravens called in alarm and flew to the battlements. Next to LC, who was gripping the ops table, there was something wrong with Brenda. Her body spasmed as the banner magic woke the Viking blood sleeping in her veins, transforming her into a snarling berserker. In moments, her uniform hung in tatters, drool fell from her mouth like a river and her eyes were red and wild.

The enemy was inside the Keep.