Henry's Tunnel is the nickname given to the tunnel on the Main Line near Ballahoo. It got its name after Henry was abandoned there in 1922, claiming he did not want the rain to spoil his "lovely green paint with red stripes".
In the Railway Series, Henry's Tunnel was originally single-bored until Henry was bricked up inside it and a second tunnel was bored alongside.
- Henry once got stuck in the eastern bore.
- So far, two engines have hidden in Henry's Tunnel; Henry and James.
- Some time around the eighth season, the bore that Henry was shut in gained a second track.
- In the fifth season, one of the bores was re-gauged for the Skarloey Railway engines.
- A signal box has appeared and disappeared at the portal since the seventh season.