New track was built for the Heathrow Express, it opened in 1998. 2 × 5 miles of tunnel, plus a bridge/flyover to cross the Great Western Mainline. https://en.

New track was built for the Heathrow Express, it opened in 1998. 2 × 5 miles of tunnel, plus a bridge/flyover to cross the Great Western Mainline. https://en.wikipedia.org/wiki/Heathrow_Express https://en.wikipedia.org/wiki/Heathrow_Express