A special barrier that will be built to protect rare bats will cost £100m, according to the chairman of HS2 Ltd.
Sir Jon Thompson told a rail industry conference the bat protection structure in Buckinghamshire was needed to appease Natural England, as bats are legally protected in the UK.
The 1km (0.6 mile) curved barrier will cover the tracks alongside Sheephouse Wood near Calvert in Buckinghamshire, to prevent bats being disturbed by high-speed trains.