‘I’ll give you what lift I can on the pole,’ I told him, gripping it with both hands. ‘Ready?’

‘Right.’

‘Three, two, one – lift!’

Up went the black box, scraping against the sides of the shaft. Toad snapped one more length on to the bottom of the stalk and said, ‘OK – steady again.’ While I held the pole in the middle, Pav bent his knees, lowering the box on to the pad.

‘Angle-irons next,’ I said – but when I went to slot them into position, I found we still hadn’t got the box high enough. We needed another three or four inches to give us the necessary clearance. While Pav and I both grabbed the pole and lifted, Toad slipped his steel toolbox under the bottom and wedged it there. That gave us the space we needed; I got the struts into position, arranged some bubble-wrap padding on top of them, and called to the others to lower gently.

All that had taken a lot of effort and concentration. When I checked my watch I was amazed at how much time had gone by. Our torch batteries were faltering and needed changing.

‘Got to keep moving,’ I said as we took a quick break for a drink of water. Our next task was to chip out a gully for the co-ax cables that would connect the SCR to the device – another aggravating job at which only one person could work. Again we took it in turns, going all out for a few minutes, then resting. As soon as we had a channel clear Toad moved in to connect the cables, and we went back to our main excavation.

I’d realised that our best plan was to form the spoil from our cavity into a ramp, so that we’d be able to slide the Apple components up it and into position. The trouble with this was, the ramp itself began to get in our way. Digging became progressively more awkward as we had to lean over our own heap to reach the back of the recess. By the time we had a hole of the right dimensions, we were both knackered.

All this time, when he wasn’t tinkering with the cables, Toad remained bent over his charges, tightening, adjusting, listening through his headphones. Then, as we paused, I noticed he was into his hand-washing routine again, a curious look on his face.

‘What’s the matter?’

‘Just trying to imagine it all white in here.’

‘White?’

‘When the device is detonated, everything in here will be vaporised in blinding white light.’

‘Charming. I hope we’re not here to see it.’

‘You wouldn’t see anything,’ he said. ‘You wouldn’t feel anything. You’d be obliterated, just like that.’ He snapped his fingers – and suddenly, as if he’d conjured up a genie, we became aware of a noise.