‘OK,’ she said.

Ben headed in the door. Brushing past her, he brusquely handed her an envelope.

‘What’s this?’ she said, surprised. She fingered it. There was cash inside. Not much, but certainly enough to get Louis a new pair of trainers. Ben shrugged, embarrassed.

‘Your mum told me that place you’re working isn’t going to last the month. Figured you could do with it till your benefits come back on stream.’

Pearl stayed outside a second or two longer in amazement, clutching the envelope and listening to Louis doing tiger-roaring inside, till the sausages started to burn. God, even Ben knew the business was doomed.

‘What would you say,’ Austin was saying the following day, trying to finish off an email to his grandmother in Canada while also transporting a petulant Darny down the busy street. ‘What would you say your favourite things are right now, D?’ Darny thought about it for a bit.

‘Ancient martial arts secrets of ju-jitsu,’ he said finally. ‘And the Spanish Inquisition.’

Austin sighed. ‘Well, I can’t tell your grandmother that, can I? Can’t you think of something else?’

Darny thought some more, dragging his heels on the pavement.

‘Snowboarding.’

‘What do you mean, skiing? You’ve never been snowboarding.’

‘All the kids at school love snowboarding. They say it’s totally rad. So I suppose that’s the kind of thing you’d like me to like. So just say that, it hardly matters.’

Austin looked at him warily. Darny’s school was good, and the area they lived in had got markedly posher in the last few years. There were more and more children who had more than Darny, and the older he got, the more he was starting to notice.

‘You probably would like it,’ he said. ‘We should try it one year.’

‘Don’t be stupid,’ said Darny. ‘One, you’d never take me, two, I’d hate it, and three, you have to wear moronic hats. Moronic,’ he said, enunciating clearly in case Austin had missed the point.

‘OK,’ sighed Austin, just typing in ‘skiing’ on his BlackBerry. It wasn’t like his grandmother could make it over to check. She was old, he realized, that was true, and devastated by the loss of her only son, but after that, it was as if she’d had the great tragedy of her life and therefore was excused from doing anything else: she hadn’t ever seemed to be the least bit interested in the progress of her grandchildren, apart from the occasional passing query and a very small cheque at Christmas. Austin had given up trying to understand it. Families were funny things, no matter what size. He squeezed Darny to his side.

‘Hey!’ said Darny. Austin turned his head. ‘Sirens!’ shouted Darny. ‘Fire engines! I think we should go see. I want to see.’

Austin smiled. Every time he thought Darny was turning into a sullen teenager way too quickly, the ten-year-old in him reared its head. As ever, though, Austin wanted to hold back. Once upon a time, those sirens had been for their parents. He lived in constant dread of witnessing it happening to someone else.

‘We shouldn’t, D,’ he said, trying to steer him in the direction of a local sweet shop.

‘Fire engines,’ said Darny. ‘You can tell Grandma it’s fire engines I like the best.’

Pearl, deep in thought, and Issy, likewise, felt the crumping sound as well as heard it; it was extremely loud and startling in the quiet Saturday morning air. A large, twisted metal noise, punctuated with shattering glass, then sudden screams, and car alarms, and horns beeping and tooting furiously.

Along with the two customers, both young studious males who had plugged their laptops into the walls and had been enjoying the free wifi and electricity for over forty-five minutes, one on a small latte and one with a bottle of sparkling mineral water, they charged outside to the entrance to Pear Tree Court.

‘Oh no,’ said Issy, stopping dead in her tracks.

Pearl was grateful Louis was home with her mother, and felt her hand fly to her mouth.

Strewn right across the road, as if dropped from the sky by a bored child, the bulk of the number 73 – the huge, elongated, unloved bendy bus – lay smashed and on its side. It blocked the road completely, its true size suddenly laid bare, as wide as the height of the house, and as long as half the road; the smell of wrecked machinery was horrifying; smoke rose from the undercarriage, a mass of exposed metal and piping.

A cab with its roof bashed in had come to a stop, skewed at a crazy angle across a reservation. Behind it could just be glimpsed a dirty white Ford Escort that had ploughed straight into the back of it. And most ominously of all, several metres in front of the top right corner, as if hurled there, was a twisted, bent bicycle.

Issy felt sick, her heart pounding in her chest. ‘Christ,’ she could hear one of the laptop boys saying. ‘Christ.’

Issy felt in the pocket of her apron for her mobile phone. She glanced, light-headed, at Pearl, who had already found hers and was prodding 999 into the handset.

‘Quick,’ said the other man. ‘Come on! We have to get them out.’

And Issy glanced up, as if in slow motion, and saw the bus was full of people – shouting, waving, clawing people. Others were already running from shops, from the bus stops, from houses, to help. In the far distance, the first siren could be heard.

Issy picked up her phone again.

‘Helena,’ she gasped into it. She knew her flatmate had a day off – a precious day off – but she was two streets away.

‘Hmm?’ said Helena, obviously still half asleep. But within two seconds she was wide awake and pulling on her clothes.

At one end of the bus, people were hammering on the window; it didn’t seem to be breaking. With the smoke seeping out of the pipework, Issy wondered – everyone wondered – if the engine was going to explode. Surely not. But there had been stories about these buses catching fire, everyone knew it. Anything could happen. In the middle of the bus, a tall man was desperately trying to open the doors from the inside, above his head. One of the men from the coffee shop was already clambering up the side of the bus – what had been the roof, but was now the side – and other people were anxiously shouting guidance to him. From inside the bus Issy could hear screaming; the driver looked unconscious.

There was a scream from a woman halfway down the road. A young man – obviously a cycle courier, in skintight lycra, now ripped, with a huge walkie-talkie still on his hip – was lying, eyeballs rolling, in the gutter, his arm at a very strange angle. Issy looked over her shoulder and was relieved to see Helena tearing down the road at full pelt.