Bailiffs are continuing to try to remove anti-HS2 protesters from tunnels by Euston station, after a demonstrator attached himself to the structure.
A group of at least six activists have spent more than a week in a network of tunnels beneath Euston Square Gardens.
Dr Larch Maxey, one of the demonstrators, said on Thursday that bailiffs had dug a parallel “down shaft” and connected it to the protesters’ one.
Eviction efforts continued on Friday as bailiffs tried to remove another environmental campaigner from a “lock-on” at the bottom of a down shaft.
The demonstrator, Lazer Sandford, attached himself to a tunnel using a device made of steel and concrete around his arm.
HS2 Rebellion group, an alliance of groups and individuals campaigning against the scheme, said on Friday that Lazer remained in place, estimating it would take several hours before the device could be opened.
They added that another lock-on device was attached to his ankle.
In a statement from HS2 Rebellion, Lazer said: “I’m only doing this because I don’t have a choice.
“I shouldn’t have to, but we are now in a total emergency. The lives of people in my generation are being risked by carbon-guzzling vanity projects like HS2.
“HS2 uses huge amounts of high carbon steel and concrete and it will only make the climate emergency worse.”
Roc Sandford, father of Lazer and 18-year-old Blue Sandford, another protester in the tunnels, said he was “scared and distressed” as their parent but was “right behind them” and understood “exactly why they know they have to do this”.
Emailing the PA news agency from his home on the Hebridean island of Gometra, he said: “HS2 needs to be put out of its misery.”
Mr Sandford said he speaks with his children “regularly”, describing them as “completely resilient, upbeat and brave”.
He said Blue and Lazer had helped him on previous protests against Scottish salmon farming, which “had a big impact on them both”.
The family have also protested with the environmental campaign movement Extinction Rebellion.
Commenting on the tunnellers he said: “I am in awe of all of those incredibly brave spirits down there, not just my children, but all of them.”
Confined space rescue specialist Peter Faulding said the eviction could last up to “six weeks” and end up costing “millions of pounds”.
Mr Faulding, founder of Specialist Group International and an expert witness for the protesters’ legal team, criticised the handling of what he alleged was a “rushed” operation.
Speaking to PA, he outlined the scale of the challenge facing bailiffs: “They’ve got to dig that tunnel, they’ve got to follow that tunnel and they’ve got to dig it it out to at least well over a metre and shore every inch of it up to be safe.
“This is unstable ground. So you’re looking at a very slow operation.”
Mr Faulding, who worked on a number of tunnel protest evictions in the 1990s, said the situation in Euston was a “public relations nightmare” for HS2, that “could have been done so much better”.
He warned eviction was going to become “extremely difficult and extremely dangerous”, with the potential for someone to get “badly injured”.
Mr Faulding said air monitors were “vital” in the tunnels to avoid the risk of hypoxia and “hardwire” communications were needed to maintain contact in case there was a tunnel collapse.
On Friday, staff could be seen removing buckets of mud from the tunnel while several police officers remained around the perimeter of the site.
HS2 Rebellion has called on the Government to scrap the “expensive, unpopular and destructive” scheme.
The environmental campaigners are attempting to protect the green space, which they claim will be built over with a temporary taxi rank before being sold to developers as part of plans for the high-speed railway.
Activists in the tunnels include veteran environmental campaigner Swampy, real name Daniel Hooper, and his son Rory.
Earlier this week a High Court judge rejected a legal bid to halt efforts to evict them.
Mr Justice Robin Knowles refused an application brought by Dr Maxey for an injunction requiring HS2 and others to cease operations.
An HS2 Ltd spokesman said: “The safety of those trespassing and that of the HS2 staff and emergency service personnel in this operation is of paramount importance.
“We are doing all we can to end this illegal action safely, and progress has been made with access secured to the underground tunnel.
“As has been reported this morning, the illegal trespassers have attached themselves underground, which increases the danger to themselves, but also to our team and the emergency services.
“The High Court this week issued an order to require the illegal occupiers to leave their tunnel. Dr Maxey still hasn’t complied with the court order, which also told him to provide information on the tunnels and its occupants.
“We urge Dr Maxey to comply with the order as soon as possible – for his safety and the safety of the other activists and the HS2 staff and agents tasked with removing them from the danger they have put themselves in.”