The Tunnel under Fort Regent was opened on 25 February 1970, after being approved on 19 February 1963. It was designed to ease the flow of traffic across St Helier from east to west and back across existing congested routes. It is a single-bore tube linking Route du Fort with Route de la Liberation (the Weighbridge).
The total cost of creating the tunnel was £441,550, including the £110,000 land acquisition costs for either end. It was built in 1968 and 1969, and officially opened on 25 February 1970 by the Bailiff, Sir Robert Le Masurier, who was then driven through by Senator Leslie White, president of the Public Works Committee.
It is 830 feet long, 29 feet wide, 22 feet high, 50,000 tonnes of stone was removed from under the Fort and 4,000 cubic yards of concrete was used. The Tunnel was constructed by Edmund Nuttall, Sons and Co (London) Limited. The Explosives Magazines at Crabbe were originally created in 1968 for storing the explosives required for forming the Fort Regent Tunnel. The Consulting and Chartered Engineers were "G Maunsell and Partners".
The western approach was once part of "Le Chemin du Quai", part of which still exists and is part of Ordnance Yard.
The Cedars Flats were built upon the site of Gothic House and The Cedars. They were acquired for safety reasons in connection with blasting for the tunnel and because The States could not tunnel under someone else's land. The same applied to the other end of the tunnel where several properties were acquired on Pier Road, followed by the building of Clos du Fort flats.