Tree-top protesters opposed to the construction of the HS2 train line yesterday revealed their plan to escape eviction by camping out in a 100-foot tunnel that they had secretly constructed under the streets of London. Bailiffs descended on the protest at Euston Square on Wednesday morning, where people have been living in 80-foot-high treehouses, tents, and pallet shelters since the summer. The protesters want to protect what they describe as “some of the most historic trees in Central London,” which they say are at risk from the construction of a temporary taxi rank. That taxi rank will serve Euston Station while the current rank is demolished to allow construction of the high-speed rail hub that will ferry passengers to Birmingham New Street. The protest group, called Hs2 Rebellion, say that they have spent several months constructing a 100-foot tunnel, complete with wooden joists and boards, where they believe they can hold …