TOP TEN SEVERN TUNNEL FACTS
At 144ft below sea level, the Severn Tunnel is the lowest point on Britain’s railway network.
It was the world’s longest underwater railway tunnel, at 4 miles 624 yards, until Japan’s Seikan Tunnel opened in 1988.
It was the longest tunnel on Britain’s railway network until the Channel Tunnel Rail Link from Ebbsfleet to London St Pancras opened.
The Severn Tunnel took 13 years to build and opened in 1886.
The ‘Great Spring’, a source of fresh water on the Monmouthshire side, flooded the workings twice during construction, first in 1879 and again in 1883.
The Great Spring was sealed in 1880 behind watertight doors; these were accessed by diver Alexander Lambert using Henry Fleuss’ new self-contained breathing apparatus.
Some 50 million tons of fresh water from the ‘Great Spring’ are pumped into the River Severn every day.
The pumps were steam powered until the 1960s; today, they’re electric.
Chief Engineer Sir John Hawkshaw advocated the abolition of the GWR’S broad gauge.
The GWR launched a motor-rail service between Pilning (Gloucestershire) and Severn Tunnel Junction (Monmouthshire) in 1924; it ended when the Severn Bridge opened in 1966.