Officials blamed dry weather followed by torrential rain at the weekend for the subsidence of a section of the Cake Hole tunnel, rather than their own digging.
The remaining protester Matt Benson, 24, and one of the professional tunnellers employed to remove him - the so-called men in black - were cut off 25 feet inside the tunnel entrance for five hours. They could be seen by rescuers and were passed food, water and air supplies. Although they were thought able to scramble out unaided, it was decided this could have caused further collapses.
Other tunnellers helped to shore up the walls before the two men were brought unharmed to safety, in what officials described as a "rescue rather than an emergency".
The collapse of the tunnel - on what was likely to be the last day anyway after Mr Benson, a former NHS administrator, had intimated he would come up yesterday morning - overshadowed the end of the lengthy pounds 4m eviction. For the authorities it vindicated what they have said in the past about the risks of this form of direct action.
Inspector Rick Hollinshead, of Cheshire police, pointed to the "inherent dangers" of such tunnels and suggested that they may not be used in future.
The Under-Sheriff of Cheshire, Randal Hibbert, said: "It is very fortunate indeed the incident was not more serious. The protesters place not only their own lives in danger, but those of their rescuers. I hope a lesson has been learnt."
Jeff Gazzard, one of the protest co-ordinators, said it was curious the tunnel had collapsed on what was going to be the last day of the protest, and that a "rescue" was needed. He said all involved knew what they were doing. "The protesters are well aware of the risks."
The campaign against the pounds 172m runway had been a "success" and was part of an economic war of attrition which involved hitting the construction and airport authorities in their pocket - "the only language they understand". He predicted that airport authorities around the country had learnt their lesson. About 150 people have been removed from the 1,000-acre Bollin Valley site - occupied since January - many of them in a variety of tree houses and tunnels which were refined versions of those used in earlier actions such as Fairmile in Devon.
Mr Benson had stayed17 days underground, more than twice the time that Swampy spent down a tunnel at the A30 site. Meanwhile, Mr Hibbert was "relieved" the eviction was over. "By and large it has gone very well," he said.
After the fury of the first day's eviction, when some of the sheriff's officials were accused of assaulting protesters and at least one journalist, the process has been mostly calm and involved a great deal of unseen co-operation between officials and campaigners.Reuse content