Every window in their car – and the cars surrounding them – shattered with piercing shrieks. The rusted Astra three cars ahead flew out from the flames, knocked aside like a golf ball from its tee by the raging fireball at its side. The ground trembled so much that Kate was sure their own wheels left the tarmac. She watched the Astra smack the line of trees at the side of the motorway; it had landed behind their car, suggesting the explosion had happened in front of them. The smoke mirage faded from the crater ahead, and she saw what had fired the shell. It was half a mile beyond the overhead bridge in front of them, crunching its way over the dead vehicles in its path.

‘Bloody hell,’ yelled Mark, ‘that’s an actual bloody tank!’

It’s a Challenger 2 . Ewan was in my English class, and did tanks for his Speaking and Listening presentation .

It had been the only presentation delivered with any enthusiasm, so it was the only one that stuck in Kate’s memory. She mainly remembered the worst parts: that it could kill from up to five miles away, and that the only thing ever to destroy a Challenger 2 had been friendly fire from another Challenger 2.

‘How the hell did Marshall get his hands on one of them?’ asked Mark.

‘I don’t think anyone tried to stop him,’ she whispered.

Mark seemed to not hear her answer – or more likely did not care – as he found a way around the crater and continued their path along the M1, straight towards the tank.

Simon made a yelling noise in the back seat.

‘Yes, we’re going towards it,’ Mark muttered. ‘If we retreat it’ll get us for sure, or chase us back to Harpenden. If we go towards it, there might be a one per cent chance we’ll get inside its range.’

Kate didn’t mind the odds being against her survival. Not at that moment. Her intellect told her she could still contribute to this war, but the rest of her brain told her she had nothing left to offer.

‘And yes,’ Mark muttered, ‘I know about its secondary weapon. But I’d take my chances with the chain gun over those shells.’

Ahead, the tank surged over another row of cars. Kate watched as the first car – a large black people-carrier – crumbled and flattened in submission. Her parents’ lawnmower had never cut grass as efficiently as the Challenger 2 mowed its way over a carriageway of vehicles.

The tank fired a second shot, which smashed into the brow of the bridge above before it could reach its intended target. Half a tonne of concrete left the bridge, flew through the sky and tumbled its way into the nearest caravan, which exploded over all four lanes like a wood and metal supernova.