Rosa was still mesmerised by all the sights. She could now see the giant Ferris wheel they called the London Eye. Alice had already told her that it cost seventy million pounds to erect and was the most popular paid attraction in the country.

Rosa had never been on a Ferris wheel. And she’d never been to a fairground either. She remembered her father telling her that he was going to take her to one. But that was a week or so before he was murdered alongside her mother, so it never happened.

Rosa noticed a crowd of people up ahead. There were also several police officers in yellow jackets.

‘This is the place,’ Alice said. ‘It’s called New Scotland Yard and is probably the most famous police headquarters in the world.’

Rosa felt her back stiffen.

‘It’s not usually like this, though,’ Alice said. ‘I wonder why …’

And then they saw the flowers and the television camera crews and it dawned on both of them what was going on.

‘Oh God, these flowers are tributes to the Commissioner who was shot yesterday and those other policemen,’ Alice said. ‘Don’t they look beautiful?’

Rosa opened her mouth to speak, then snapped it shut. She wasn’t sure what to say or how to react. But she did know that she had to remain calm, that there was no need to get anxious.

Alice pulled on her hand so that they could have a closer look.

Rosa was surprised at how many flowers had been laid here and at the number of people who had come to look at them. She guessed there were over a hundred, and some were in tears.

The building itself also surprised her. It had an art deco façade and looked more like a luxury hotel than a huge police HQ.

Alice let go of her hand and crouched down to read some of the cards that people had attached to the flowers.

While she did that, Rosa looked around, and it occurred to her that she was responsible for all of this. It didn’t make her feel guilty. Just strange.

She had killed more than fifty people in total and had never stayed around long enough to see first-hand the grief she’d left behind. This was another new and sobering experience.

Alice stood up, took a tissue from her bag, and dabbed at her eyes.

‘It’s easy to forget what’s happening when you’re not watching the telly or listening to the radio,’ she said. ‘I feel like I’m at a funeral.’

Rosa put an arm around her and pulled her close. Then she turned to kiss her forehead. As she did, she happened to catch sight of a woman who had just walked out of the building through the glass doors. She had brown hair and was wearing a black trench coat.