Three paramedics came into the reservoir with me, once I’d persuaded them from their tea and Garibaldis in the St John Ambulance tent at the fair, and convinced them I wasn’t some mad person who had jumped in a water butt, and there really were two injured men down in the disused Hornsey Wood Reservoir, under the park. The paramedics were two big burly women and a jolly bloke with a very kind face. We all did a half run/half walk back to the hatch; the ambulance parked next to the tent that kids had been climbing in all afternoon arriving minutes afterwards.

Dad had a sprained ankle and a slightly battered face. Kemp’s injuries were a lot more serious. He had fallen while trying to rig up a caving light from the top of one of the arches and had cracked his head open on some brickwork. It was a good job I never saw all the blood. Like Humpty he needed to have his head put back together again. He was in hospital for three weeks, the first week of which he was mostly unconscious (I spent a lot of time just sitting and watching his face and its contours as he slept), but he’s made a full recovery, apart from a scar by his temple, and is back retelling bad jokes and laughing that laugh of his.

We have all been called ‘stupid idiots’ by the paramedic team, and the hospital staff and Haringey Council, who’ve given us a proper ticking-off, and Kemp is all disgruntled because he doubts he’ll be able to get down there again, now, and he only got a few decent photos. Still, one of those photos won the Architectural Photo of the Year – it was in the Evening Standard, along with his real name, Jason Hamilton – and he’s alive, which is the main thing, plus he was quite impressed by my heroic escape from the reservoir. How I walked the twenty-four arches. Very impressed, as a matter of fact.

‘Can I ask you to put your blind up now, please?’

I smile at the air hostess and slip my pencil back into the little pencil case I have in my travel bag. The duty-free trolley has made its final trundle up the aisle and is disappearing behind the blue curtain. Disembarkation cards are being retrieved by yawning passengers from under dog-eared magazines in the seat pockets in front of them. Airline staff are smiling wearily at each other, smoothing hair back from faces above tired eyes and getting ready to get strapped into their side-saddle seats. Others do final checks of trays, blinds and seat belts.

We’re landing in twenty minutes.