Knox and Williams had visited the festival, along with everyone else in the city it seemed, over the summer of 1951. It was a welcome distraction from their office hours spent monitoring the swelling ranks of American and Russian agents treating London as their playground, all the while wondering if the stalemate along the 38th parallel would break and turn Korea into another world war.

Only the Royal Festival Hall was left standing now. The rest of the festival grounds had been cleared for redevelopment. So far only the new twenty-seven-storey headquarters of Royal Dutch Shell had started to rise in Skylon’s place.

He crossed over Blackfriars Bridge, stopping briefly to feel the wind blow past him. Even on the most stifling days, the air still moved on the Thames. He watched a heavy barge float downstream and under the bridge to the docks that lined the south side of the river from Blackfriars to beyond Tower Bridge.

He didn’t know what he was going to say to Holland, but he wanted to see him. Maybe sitting with him would help him accept how easily he’d let himself be manipulated, or maybe it would push him to do something about it.

Knox had visited Holland in Guy’s hospital every evening since he’d been rushed there from Highgate. Every evening except yesterday. The nurses who worked nights had no idea how Knox managed to appear at Holland’s bedside out of thin air at the start of their shifts. They’d just check Holland’s private room during their rounds, and suddenly he’d be there. Then, ten minutes or an hour later, they’d look in again and he’d be gone.

The hospital was busier than Knox was used to this afternoon. Visiting hours were in full swing and wives, husbands, parents, and children swarmed through the building. The grown-ups looked worried, resigned, or dog-tired. The children either stared excitedly at their unusual surroundings or ignored them.

Every bed Knox passed on his way to Holland’s room had someone next to it, talking, fussing, or just sitting quietly. And so did Holland’s.

Sarah Holland hadn’t slept properly in days. She’d found her husband lying face down on a thick-pile rug in their living room when she’d come home on Sunday evening after an afternoon visiting friends, his body limp, eyes closed, and breathing shallow and slow. She phoned for an ambulance, then she phoned Leconfield House. And for the last week her whole life had consisted of sitting at her husband’s bedside for two hours every morning and afternoon, and the rest of the time sitting at home, waiting to come back to the hospital, or for someone at Leconfield House to call and tell her something.

‘Sorry, I didn’t realise you were here,’ Knox said, as the door clicked shut behind him. ‘I’ll leave you alone.’