This tunnel is unique because its the only one in the world that has a road bridge crossing directly over it!

Installing special lights at the height where most train passenger windows are located is not beyond reach, indeed the Severn Tunnel gets closed for engineering works and maintenance so such an installation is definitely possible.

At the moment, because of the loss of GPS signals in the tunnel, the only way to pinpoint exactly the point directly under the Prince of Wales bridge is by using a stopwatch.

Such an installation would only temporary divert rail traffic, and rail passengers can use alternative transport to get to South Wales (ironically, by passing over the tunnel on the road bridge)!

Together, this is a dream which can easily be turned into a reality.