At the bottom of the shaft, the tunnels open. The scale is astonishing. The familiar tunnels of the Tube look like narrow rabbit warrens in comparison. It is a Jules Verne landscape. Even unfinished, even in the dim light of the industrial lamps and with dust and dirt collecting thickly under your collar and hard hat, the tunnels are spectacular. And they are getting bigger.Ada, Phyllis and their sisters could only do so much. Now that they have done the heavy work, a scavenger party of diggers, drillers, forklifts and loaders is widening the tunnels. There are 20 or more of them down here, some dormant and covered in  thick dust, others crashing and crunching into the concrete casing left behind by the TBMs. They were once JCB yellow, but anything left down here takes on the dry colour of the dirt and dust.

I watch as one of these yellow raptors, with a long mechanical arm ending in a serrated claw, gouges chunks out of the tunnel, widening it by several metres. Even with earplugs it is deafening. The roar of the plastic air vents, bloated anacondas that pump dusty air from tunnel to surface, makes the shouted instructions of my guides redundant. The army of engineers in orange boiler suits — and whatever the sex of the boring machines, their operatives are all men — have a language of hand gestures, signalled through thick gauntlets.

Coming up for air, stepping out onto Charterhouse Street into bright sunshine and the lunchtime rush, is dizzying. Do the office workers know, as they race for a sandwich, that the earth is being stolen from beneath them?

The old Farringdon station, dwarfed by the blue hoardings, is still open and the Metropolitan Line takes me home to Paddington in half an hour. It will be eight minutes on Crossrail.

I have a particular interest in this behemoth project, as Crossrail runs directly beneath my street. Shortly after I moved in, a man in a blue Crossrail jacket came to my flat with a spirit level and a tape measure to make a record of every crack in the plaster — down to the tiniest hairlines inside the airing cupboard. If the building falls down, no one can accuse Crossrail of not exercising due diligence. In the nearly four years I have lived here, they have dug up the road three times. The most recent round started this past summer. The drills sound an alarm at eight o'clock in the morning and go on until six. I am writing this in my bedroom at the back, headphones clamped over my ears. Whatever my objections to the immediate noise and disruption, I am awestruck by the ambition of this deepest of London's railway lines. It is exciting to have one's foundations shaken. If I had lived on Sussex Gardens in 1863, in what would have then been a spanking new house, not the crack-prone terrace broken into flats that it is now, I would have felt a similar thrill.