‘It’s not in the school,’ she said. ‘It’s under it – where the train tracks are. And it’s a he.’

The school she was talking about was the local comprehensive, Acland Burghley, where countless generations of the Peckwater Estate had been educated, including me and Abigail. Or, as Nightingale insists it should be, Abigail and I. I say countless but actually it had been built in the late Sixties so it couldn’t have been more than four generations, tops.

Sited a third of the way up Dartmouth Park Hill, it had obviously been designed by a keen admirer of Albert Speer, particularly his later work on the monumental fortifications of the Atlantic Wall. The school, with its three towers and thick concrete walls, could have easily dominated the strategic five-way junction of Tufnell Park and prevented any flying column of Islington light infantry from advancing up the main road.

I found a parking space on Ingestre Road at the back of the school grounds and we crunched our way to the footbridge that crossed the railway tracks behind the school.

There were two sets of double tracks, the ones on the south side sunk into a cutting at least two metres lower than those to the north. This meant the old footbridge had two separate flights of slippery steps to navigate before we could look through the chain link.

The school playground and gym had been built on a concrete platform that bridged the two sets of tracks. From the footbridge, and in keeping with the overall design scheme, they looked almost exactly like the entrance to a pair of U-boat pens.

‘Down there,’ said Abigail and pointed to the left-hand tunnel.

‘You went down on the tracks?’ asked Lesley.

‘I was careful,’ said Abigail.

Lesley wasn’t happy and neither was I. Railways are lethal. Sixty people a year step out onto the tracks and get themselves killed – the only upside being that when this happens they become the property of the British Transport Police, and not my problem.