The trance was only broken when, in a stoned voice, I told Charlie her skin was ‘softer than kitten’s fur’ and she roared with laughter, and then I did too and within moments we were rolling about literally clutching our sides, barely able to breathe.

‘Ha, ha, bonk,’ I said, when I was able to get some air into my lungs.

‘What?’

‘It’s the sound—’ A convulsion of laughter stabbed at me. ‘The sound of a man laughing his head off.’

That set us off again.

Eventually, when we’d come down and calmed down, Charlie lay on her front beside me, legs crossed at the ankle, showing off the small mermaid tattoo on her right ankle, and said, ‘Can you get your sister to come up to London on Saturday?’

‘I expect so? Why?’

She laid her head on one side and smiled. ‘I have a surprise for you.’

Charlie asked me to meet her by the London Eye at noon. At Victoria station I steered Tilly through the vast crowds, many of them apparently heading to a football match. Tilly and I stopped en route to the taxi to grab a doughnut, my treat.

‘What’s all this in aid of?’ she asked in the back of a black cab.

‘The doughnut?’

‘The excursion! You don’t invite me up very often.’

Traffic was slow and I was concerned we’d be late to meet Charlie. No matter how much I’d begged, she wouldn’t tell me what she had planned.

‘Andrew?’ Tilly said.

‘I just thought it would be fun for us to spend a day together. Plus I want you to meet Charlie.’

‘Wow. You’ve only known her for two minutes.’

‘Yeah, but . . .’

‘Oh. Em. Gee.’ Tilly put on a silly voice. ‘My big brother is in el you vee.’

‘Stop it.’ But I knew my face must have gone pink. I groped for something else to say. Although Tilly seemed amused, I was worried that flaunting my new relationship, when I was supposed to be helping to cheer up my recently dumped sister, was going to have the reverse effect.

We sat and watched the scenery roll by, a thin mist giving the London streets a soft-focus Saturday morning sheen. The cab dropped us by Borough Market. We were early and I wanted breakfast, so I bought us each a bacon roll, which made Tilly moan with pleasure, before heading down to the South Bank.

‘Doughnuts. Bacon rolls. Is your plan for today to fatten me up and sell me to a hungry troll?’

‘Damn. Rumbled.’

It was bitterly cold by the river and the Thames was the colour of a bruise, but the icy wind was invigorating, a wake-up slap that made my nose run and my eyes sting.

‘Dad would have said this was brass monkeys,’ Tilly commented.

‘Are you too cold?’ I asked.