Inside HS2: Meet London's tunnelling miners

It is loud, dusty and 30m (about 98ft) underground - this is the domain of the London miner.

We are on a tunnel boring machine (TBM) inside High Speed Two's huge Northolt tunnels.

These tunnel-boring machines are part of a tunnelling renaissance that is creating a new, mainly hidden, London.

They have been used to drill the Silvertown Tunnel, Crossrail, the Power Tunnels in north London and the Thames Tideway or super sewer as well as the Channel Tunnel.

Operating these machines are teams of miners who come from all over the world and move from project to project.

The miners are a pretty unassuming lot and don't really think what they're doing is unusual.

They work shifts of anything between seven and 12 hours. The TBM does not stop, crawling along at 16m (about 52ft) a day and runs 24/7.

Graham Clark and his son Liam are from Kent.

Graham says he first got into mining due to the Channel Tunnel: "I was just asked if I wanted to go down the tunnel being a local labourer."

He says he carried on ever since, after getting six years' work on the Channel Tunnel.

Liam says: "My old man got me into the game. I just finished school, I got a phone call he was working away at the time, he said, 'Right you're starting with me tomorrow'.

"And that was it. Worked away from home ever since then. For the last 14 years or so."

Graham says it is a rewarding career.

"It's challenging and can be hard work but you have a good crew and you all work together and everyone helps each other out. And you work for the team, different challenges but yes it's good."

Jack Doherty, like a lot of miners is from Donegal in Ireland. He says it is very much like any other construction site.

"There's a big tunnelling community back home where I'm from," said Jack.

"A lot of the young lads here, most of their dads are in it. It runs in families a bit from where I'm from anyway it does. "

At the mouth of every tunnel there is a small shrine to Saint Barbara, the patron saint of miners.

To get to the boring machine we are driven for an hour in a buggy in the tunnel. It can quickly get hot down there.

The Northolt tunnels are currently 93% complete.

We visited when they were hours from breaking through to the shaft at Greenford.

Four machines were homing in the shaft from the south-east and the north-west with huge conveyor belts taking the spoil along the length of the tunnel.

These machines will then be hauled out and decommissioned.

Michael Greiner is the head of tunnelling at SCS JV.

I met him previously at the start of the project where he told me that "a lot of things have gone well but in tunnelling there's also exciting things" such as the "quite heterogeneous" geology.

He said: "We are mining along the London Basin and so geology from chalk, flint, a mix of sand.

"The geology has some surprises so you never know exactly what is happening underground, so it kept us busy."

The TBMs are hugely complex pieces of kit and the ground conditions have caused some problems.

Underneath Ruislip Rugby Club they hit sandy ground which caused large clouds of foam to end up on the rugby pitches which had to be closed.

At the time Jatin Radia, the club's chairman, told us: "The reality is it does cause further concerns because you've got local residents, local rugby club members. They're naturally concerned about what's going on and asking, 'Is it safe?'."

Drilling did continue after a pause.

In the most part no-one above ground had any idea what had been going on beneath them, according to HS2's head of delivery, James Leeming.

"A lot of people who live in west London, we may have mined 25m (about 82ft) beneath their houses and their places and their streets and they wouldn't have been any the wiser as to what was going on down here," he said.

He thinks the success of the tunnelling so far bodes well for completing the tunnel to Euston.

"It's really positive to achieve what we have done on this section of the tunnel, but we have still got an awful lot to do both this year and it's going to one of the most productive years on the civil contracts.

"This really sets us in a good place for delivering the Euston Tunnel."

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