Nick Pigott visits a former Great Central Railway tunnel that has been repurposed as the world’s longest indoor vehicle test track.
The decision of HS2’s designers not to use the majority of the former Great Central route has not stopped the GCR’s Catesby Tunnel from having a high-speed future of its own.
At almost 1¾ miles, Catesby was the longest bore on the Marylebone-Sheffield main line and is once again breaking records as the longest indoor vehicle test track in the world. It was built in the late 1890s just north of Charwelton in Northamptonshire and, despite more than 50 years of neglect following closure in 1966, its straight alignment and constant gradient of just 1:176 made it an ideal choice when Aero Research Partners began seeking a suitable site for an aerodynamic test facility.
Since 2018, the tunnel has undergone a multi-million pound investment to pump it free of floodwater, seal its ventilation shafts and refuges, refurbish many of its 30 million bricks, waterproof its roof, illuminate its walls and lay a super-smooth road surface along most of its length (the last 70 metres at the north end have had to be closed off as a roost for protected bats).
Sealing of the five vents was necessary to create the consistent temperature and humidity levels demanded by car and racing bike manufacturers, while air doors and fans regulate draught-proof or wind-tunnel conditions as required. As a result, the temperature inside the tunnel remains at around 11 degrees Centigrade all year round.
A headquarters and innovation centre has been established on the site of Charwelton station by operator Catesby Projects and – in a pleasing nod to the tunnel’s steam-age past – turntables have been installed at each end to rotate vehicles in readiness for their return runs.
The tunnel began its new lease of life in 2021 and has since seen numerous highperformance cars put through their paces, the fastest so far being an Aston Martin Valkyrie with a maximum of 260kph (162mph).
Even the designers of the high-speed tunnels now being bored a few miles west of Catesby would consider that impressive… especially in a structure built before the motoring age had really dawned!
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