Channel Tunnel terms of the Concession, Eurotunnel was obliged to investigate a cross-Channel road tunnel. In December 1999 road and rail tunnel proposals were presented to the British and French governments, but it was stressed that there was not enough demand for a second tunnel. A three-way treaty between the United Kingdom, France and Belgium governs border controls, with the establishment of "control zones" wherein the officers of the other nation may exercise limited customs and law enforcement powers. For most purposes these are at either end of the tunnel, with the French border controls on the UK side of the tunnel
Channel Tunnel defence arguments had become less relevant due to the dominance of air power, and both the British and French governments supported technical and geological surveys. In 1958 the 1881 workings were cleared in preparation for a £100,000 geological survey by the Channel Tunnel Study Group. 30% of the funding came from the Channel Tunnel Co Ltd, the largest shareholder of which was the British Transport Commission, as successor to the South Eastern Railway. A detailed geological survey was carried out in 1964–65. Although the two countries agreed to build a tunnel in 1964, the phase 1 initial studies and signing