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.