the Severn Tunnel
/ðə ˌsevn ˈtʌnl/
/ðə ˌsevərn ˈtʌnl/
- a rail tunnel under the river Severn between south-west England and south Wales. It was built near Bristol between 1873 and 1886 and is 4.35 miles/7 kilometres long, the longest tunnel in Britain.