"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, after he stopped in there, claiming the rain would 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. The tunnel later collapsed but was repaired in time for the unveiling of the Thin Clergyman's bust at Tidmouth.
- The tunnel's television sets and CGI render have had numerous modifications throughout the years:
- In the first season, one tunnel bore had two tracks and the other bore had one track.
- In the fourth season, the numerous switch tracks and the siding disappeared.
- In Thomas and the Magic Railroad, there was two tracks in each bore and the tracks leading to the bores were curved, there was a track above the tunnel, and a siding and a water tower were outside one of the bores.
- In the seventh season, each bore had one track.
- A signal box and water tower has appeared and disappeared at the portal since the seventh season until the CGI switch over.
- From the eighth season onwards, both bores had two tracks.
- From the thirteenth season onwards, the tunnel appeared to get shorter as you could see through it.
- In Blue Mountain Mystery, the tunnel was seen in a flashback and it only had one track in each bore.
- From the Adventure Begins onwards, a switch track was added infront of one of the bores and signal box and the oppersite side of the tunnel, the tracks became slightly curved.