Severn Tunnel: From its creation to electrification
Work to install a customised electrified roof track has started in the Severn Tunnel as part of the electrification of the south Wales mainline.
The Swiss-made device is so advanced Network Rail has set up its own engineering course to train contractors how to install it.
The work will eventually lead to a complete closure of the tunnel in September for six weeks.
Diversions will go via Gloucester.
BBC Wales takes a look at its timeline, from creation to electrification.
20 Jul 2016
- From the section Wales