Environmental activists have held out for their second night in the Euston tunnel, but eviction officers have said the tunnel is close to gas and water pipes and that the activists are putting their own lives at risk. The tunnellers described how they constructed what is thought to be one of the largest tunnel networks to be occupied by protesters in one of the busiest parts of London without being detected. The network has two main tunnels going off in different directions from the downshaft and is said to be at least 100ft (30 metres) long. The tunnels were built over a period of several months following the establishment of a camp of environmental activists in Euston Square Gardens last August. They joined a community of street homeless people who were already camped there. Euston station is one of the busiest in London, serving trains, buses and the tube. It is on Euston Road, a main arterial through the centre of London. The Metropolitan police, British Transport Police, Network Rail, Camden council and Transport for London all denied it had been their responsibility to monitor the site for tunnel digging. HS2 said it took possession of the site on Wednesday. One of the activists, Ben Hartley, told the Guardian how the covert operation was carried out in plain sight. “It’s hardly a new idea for protesters to dig tunnels,” he said. “I’m fairly sure that the various organisations must have had an idea that something was going on.” He said the tunnel network, which he described as an “extensive protest labyrinth”, was thought to be one of the biggest of its kind. Hartley said the most dangerous time for activists in a tunnel was when bailiffs begin their excavation. He believes that at least two members of High Court Enforcement, the group carrying out the eviction, are highly trained in dealing with this type of action. He said of the digging operation: “It’s a bit like The Great Escape.” He said the main structure in which the activists in the camp lived in the months before this week’s eviction was a long, multi-roomed living space with a lockable front door. “If anyone came along who we didn’t like the look of, we just locked the front door,” he said. When the digging started under this living space, the activists piled the earth they removed on to the floor of their home. “By the end we were crouching down when we went from room to room,” said Hartley. “In some places the earth was piled 3ft high. We cut the wood to shore up the tunnel inside too so it could not be seen.” He said part of the aim of the protest was to raise awareness about the loss of a precious park in the middle of a very built-up part of the capital. “It’s a real shame that this park is being lost to build a temporary taxi rank,” he said. “We are intelligent and hardworking people and we want to raise awareness about the fact that this is part of the battle for the future of our species.” Howard Rees, a spokesperson for the tree protectors of Euston Square Gardens, said a citizens’ assembly was urgently required to address the climate emergency. “We need sensible British people to take the reins and guide us through this.” The activists in the tunnel have released footage of fractious exchanges with the eviction crew, whom they accuse of depriving them of sleep around the clock with their drilling and banging work. Larch Maxey, one of the occupiers, said this was a form of torture for the inhabitants of the tunnel. High Court Enforcement said: “The national eviction team has been engaged to lawfully remove activists from Euston Gardens. In their attempts to delay their removal, unlawful occupiers have occupied a crudely dug tunnel on the land. “We are aware through our risk assessment and their statements in various media today that they have previously experienced a collapse and water ingress to their tunnel. The unlawful activists appear to have put themselves in danger of a further tunnel collapse, and potentially of intercepting nearby gas and water pipes, leading to risks of suffocation, flooding and drowning. “To mitigate the hazards, we are using specialist air control compressors to circulate the air, and equipment to monitor air conditions. The activists have made no provision for this. We have engineers available onsite to evaluate whether the tunnel runs close to gas, water or other utilities pipes and cables.”