‘They can’t time travel, Elle. Kwesi’s super bright but a bit wild. He’s nonverbal ASD and gets frustrated when people can’t understand his signing. He’d already been in trouble with the police. Graffiti mostly. He talks in paint. Looks like his stuff’s coming out of the wall. But they made him whitewash his murals. Think they were glad he was out of their hair.’

If I talked in paint, I’d use different shades of white but I bet Kwesi loves bright colours.

‘Did he go to a specialist school to help with communicating?’

‘Yeh. Where he swapped the term nonverbal for visual. Says Visual ASD’s a better fit.’ She smiles and takes a sip of marigold tea. I tried it earlier and spat it out. Disgusting. Like drinking a flowerbed.

‘Does his name begin with the letter L?’ I say, and Ama jerks her head as if I slapped her.

‘How did you . . .’ She shakes her head quickly. ‘No. His name’s Kwesi. Means born Sunday. But we nicknamed him Leapfrog. He was county champion at triple jump.’

‘Did he do the long jump?’ I say.

‘That too.’

Big Ben and I ask at the same time, ‘What was his PB?’

‘5 metres 90.’

Big Ben shuffles in his chair. ‘89.49% for a 3-leap.’ he says. Some people don’t call him Big Ben. They call him The Human Calculator. But they’re wrong. He’s not a human calculator, he’s a human who’s super good at maths.

‘Was he training for the Olympics?’ I say.

Ama rolls her eyes anticlockwise. ‘That’s irrelevant. He went on Leap 2100 four years ago and never came back.’

‘Leap 2100 doesn’t exist,’ says Big Ben, without pausing. ‘It’s not a leap year.’

‘What?’

‘2000 was leap. The next century leap year’s 2400. Century leap years have to divide by 400, not four. The maths has to fit.’

Big Ben’s right. 1900 wasn’t a leap year either. Or 1800, or 1700. The previous centurial leap year was 1600. Ama wouldn’t know because she doesn’t study PPF. She probably studies history. Or maybe they don’t do history in 2048. Maybe they only study the present. She does something funny with her forehead so it’s parallel lines like a school exercise book.

‘So he lied?’

‘He must have invented an itinerary. That’s a lot of work,’ I say. But inventing something that isn’t true is still a lie.

Ama shakes her head. ‘He never brought letters home from school. He rarely went to school. Just remember him texting me that he was going on Leap 2100. Maybe it was code for something.’

‘Did you keep the text on your phone?’

She shakes her head. ‘I didn’t think it was important at the time.’

For a split second I remember deleting SOS L but I try not to think about it.