When the polymer that later became known as Perspex was developed in 1931, by the British scientist Rowland Hill, it wasn’t at first a viable sheet material for economic production. Dr. John Crawford at I.C.I. in Stevenston solved the problem in 1932 and a patent for what became known as the Stevenston Process was granted in August 1932, with the name Perspex coming into use in 1934.
It wasn’t long before the motor industry noticed the usefulness of the new material, better than the cellulose-based materials used before. The coachbuilder H. J. Mulliner created many ‘High Vision’ bodies from 1937 onwards, using a curved Perspex panel for a short section above the windscreen (which fabric tambour shutters could blank off). But the term ‘High Vision’ itself was first used by Offord in conjunction with Carlton Carriage in 1935. Carlton built the bodies with curved glass instead, not Perspex panels, under licence from Paul Boettcher of Germany. Two 1938-39 H. J. Mulliner Bentleys even had a full Perspex roof over the whole front compartment and they repeated this in 1947 on a Rolls-Royce Silver Wraith.
In the 1950s the coachbuilder Hooper took Perspex to a new level, creating full-length clear tops for some all-weather bodies, both fixed and detachable (made for them by Triplex). An early example is the Daimler built in 1952 for the impending Royal Tour of Australia. Other examples followed such as the Rolls-Royce Silver Wraith in July 1956 for Nubar Gulbenkian and the 1959 Silver Wraith in March 1959 for the King of Greece. In 1961 Park Ward took up the challenge on The Queen’s Rolls-Royce Phantom V called ‘Canberra’ with what would have been the landaulette portion being in Perspex (a detachable external cover is fitted when needed). A second was also built for The Queen.
The car shown here is a Daimler DK all-weather by Hooper photographed on 14 May 1957 and delivered to the Maharaja of Bahawalpur. It is one of the more dramatic uses of Perspex and more technically challenging than its use for headlamp covers and motorcycle screens. Being rigidly attached on the Daimler it needed a full-length blind to combat heat and glare. Condensation on the Perspex was prevented by ducted cold air from two blowers. Modern regulations would probably prevent such cars being built today but glass is again providing some scope for continuous clear views through a roof.