I ducked out from under it and it followed me. It wasn’t very fast – you could stay ahead of it with a brisk walking pace, but as soon as you stopped it would drift to a halt overhead and bring a little bit of the English summer to a personal space near you.

I asked Nightingale what on Earth the spell was for. He said it was a favourite of one of his masters at school. ‘At the time I thought he seemed inordinately fond of it, though,’ said Nightingale, as he watched me dodge around the atrium. ‘Although I must say I’m beginning to appreciate its appeal now.’

According to my stopwatch, the spell lasted thirty-seven minutes and twenty seconds.

Nightingale did relent and teach me an additional forma, palma, which allowed me to give people a nice evenly spread, hopefully non-lethal smack. I had Nightingale test it on me on the firing range – it feels exactly like running into a glass door.

With a high-pitched grunt the figure went down on his back in the snow. I reached him just as he reached again into his jacket, so I smacked him hard on the wrist. ‘He’ yelped in pain and I realised it was a woman and then I saw her face and recognised her. It was Agent Reynolds.

She looked up at me with bewilderment.

I heard a scuffling sound behind me and Zach yelled, ‘They’re getting away.’

Good, I thought, one less thing to worry about, and it wasn’t like I couldn’t find Kevin Nolan whenever I needed to. ‘Let them go,’ I said.

I couldn’t leave Reynolds lying on her back in the snow, with a possible concussion and/or a broken wrist. I told Zach to stay close and walked back to find that she was sitting up and cradling her wrist.

‘You hit me,’ she said.

‘Wasn’t me,’ I said and crouched down in front of her and tried to see if her eyes were unfocused. ‘You must have slipped on some ice and gone down on your back.’

‘You hit me on the wrist,’ she said.

‘You were reaching for a weapon,’ I said.

‘I’m not carrying a weapon,’ she opened her jacket to prove it.

‘Then what were you reaching for?’ I asked.

She looked away. I understood it had been an automatic reaction just like mine.

‘Hold on,’ she said and felt her nose. ‘If I fell on my back, why does my face hurt?’

‘Have you got a headache?’ I asked. ‘Are you feeling dizzy?’

‘I’m just fine, coach,’ she said and pushed herself to her feet. ‘You can put me back in the game.’ She spotted Zach and took a step towards him. ‘You,’ she said with an excellent command voice. ‘I want to talk to you.’

‘Oi,’ I said. ‘None of that. Why were you following me?’

‘What makes you think I was following you?’ she asked.