These men are miners, and more worldly readers won't be surprised to see that they indulge in a spot of arm-wrestling over a few pints. What's more remarkable is that they've come out of the ground not in the Rhondda or South Yorkshire, but in Cricklewood, north-west London. Unbeknown to homeowners in West Hampstead and St John's Wood, a shaft is being dug deep beneath their desirable foundations. Before I trigger a rush of prospectors in search of black gold, and Cricklewood Broadway echoes to the song of canaries in cages, I should add that the miners are not extracting coal. Instead, they're excavating air, creating a pristine space below ground. To supply Londoners with all their foreseeable electricity demands, a £100m subterranean corridor 20 kilometres long is being quarried, from the old Elstree aerodrome in the north to Lord's cricket ground in the south. The National Grid has winsomely christened its mighty power cable the London Connection.
It's not due to be finished for three years, but the miners have taken over a pub to throw a breakthrough party: one stretch of the dig had punched through to the next. A tough old tunnel man called Gary tells me over several large ones that the game isn't what it was. But it seems to me that the miners earn their wages - as much as £90,000 a year - the hard way. To reach the face where they are digging takes up to two hours by single-track railway, the equivalent of a halting Intercity train from the capital to the Midlands, except that this journey is below ground.
Their working conditions can scarcely be more rudimentary. You'll get a sense of this, I think, when I say that they travel in something called a "man-rider". It does exactly what it says on the tin. You sit hunched over in a clanging, un-upholstered box. The only light, from lamps in the tunnel, comes through wire mesh over the windows. The man-rider is a Black Maria, a nonce van. But if that is unrestful, the diabolical tunnelling machine itself is patently life-threatening, if operated inexpertly. At one end of it, blades rip the earth. At the other, a great pincer swings concrete panels into place to line the tunnel. To see the column of dully lustrous clay emerging is like watching London grow: the city colonising its inhospitable element.
At the party, Gary recalls coming out of a dig in Dartford some years ago and suffering an attack of the bends as he was tucking into a curry. He asked the ambulancemen to collect his food and wine. "It was Blue Nun in those days." A Harley Street specialist allowed Gary to be accompanied into a remedial decompression chamber by his meal, but confiscated the bottle. As he forked his lonely madras, Gary watched helplessly through a porthole as the consultant drank the lot.