[1] Protest tunnelling has been utilised by protestors since the 1990s in the United Kingdom.
Protests against the construction of the Newbury bypass and the extension of the A30 road in Fairmile, Devon used tunnels.
The activist Swampy was the last to emerge from the tunnel built to protest the A30, having been underground for seven days.
[1][2] Tunnelling is an effective tactic against developments as the time and cost of removing protestors from them can be prohibitive; it is comparatively easy for bailiffs to remove ground encampments and tree houses built by protestors.
[1] Construction machinery cannot drive on ground that has been tunnelled without a risk to the protestors within.