Network Rail have release a timelapse video show the upgrade work being carried out on the Severn Tunnel. The tunnel was originally built by Great Western Railway (GWR) between 1873 and 1886, linking South Gloucestershire in England to Monmouthshire in Wales. It is over 7 km long.

The upgrade work was done to prepare South Wales Mainline for electrification and opened for operation on 22 October 2016 following six weeks of work. The electrification will provide faster and more reliable services.

Watch the video here:

Read more about the upgrade:

Image by Gif absarnt at the English language Wikipedia, CC BY-SA 3.0, Link