Channel Tunnel: Five things you may not know

The Channel Tunnel is 25 years old this year.

To celebrate, the BBC was given exclusive access to see what it takes to keep the 31-mile link between the UK and France running... and unearthed a few facts which may surprise you.

The Channel Tunnel - Life on the Inside is on BBC2 at 19:30 BST on 16 and 17 October, with the first two episodes available on BBC iPlayer.