‘Fully shielded when they converted the GlowPit to a HotPot,’ said Logan, sensing my disquiet. ‘Twelve inches of lead between us and the stack. Of all the reactor-equipped Kipshops in Cardiff, none has failed any higher than a Code Orange, and that was in the Cary Grant.’

‘The control rods jammed,’ said the porter, ‘but failsafes prevailed,’ he added, with an air of disappointment.

We’d called the Duty Officer at Albion Nuclear, who initially suggested that we should wait ‘until it got really bad’ before doing something. After more urgent pressing, he concurred between yawns that someone should go down and have a look and to get back to him ‘if we thought it looked serious’.

Logan asked me to find the nearest technician on the High Octane list but the porter saved me a call.

‘We have Oliver Tiffen on the eighth floor,’ he said. ‘Nice chap. I’ll get him down.’

For emergency scrams, visual inspections or other potentially fatal situations, there was a list of sprightly reactor-savvy octogenarians for whom a fatal dose of radioactivity would not radically shorten their lives. They were paid handsomely for their services and there was a medal in it somewhere if you were needed, but owing to reasonably robust safety precautions and the low wattage of the piles, most weren’t.

Mr Tiffen appeared in ten minutes, incongruously dressed in tweeds and plus-fours, and surprisingly underage – he looked barely forty-five. True, you could be any age to volunteer, but no matter what, members of the High Octane Group had to be at half-hour readiness at all times. Oliver Tiffen stared at the gauges in the control room and grimaced as the core temperature rose a few more degrees.

‘This looks like fun and games,’ he said, donning gardening gloves, a pair of goggles and a crude telephone headset. He wore a respirator around his neck in an old bag with an oxygen bottle strapped to the front, and carried a Gladstone bag full of spanners that jangled as he walked.

‘Problematical?’ asked Logan as Tiffen stared at the service log, which looked old and mildewy and was covered in coffee stains.

‘If I’m right, we’ve got under twenty minutes before an explosion rips the building apart and scatters burning fissile material for about a thousand yards in every direction.’

‘And if you’re wrong?’ asked Logan.

‘Then it’s a failure of instrumentation or my expertise,’ he said with a grin. ‘You’d all better get clear just in case. Porter? You can stand by to flood the core chamber if I can’t shut down the reactor in time.’

‘It’s that bad?’

‘It’s that bad. Here,’ he added, passing a sealed envelope to Logan, ‘take this in case everything goes balls-down, would you?’