Dennis Specialist Vehicles was an English manufacturer of commercial vehicles based in Guildford, building buses, fire engines, lorries (trucks) and municipal vehicles such as dustcarts. All vehicles were made to order to the customer's requirements and more strongly built than mass production equivalents. For most of the 20th century Dennis Brothers was Guildford's main employer.
Following a decade of financial difficulties original shareholders sold out in 1972 and Dennis's ownership has since passed through quite a number of hands. The Woodbridge site was sold and a new small factory built in Slyfield remains in use by lineal business descendant, bus-maker Alexander Dennis. No Dennis haulage trucks have been built since 1985. The last Dennis fire engine left the Guildford factory in 2007.
The Dennis brand is still used on Alexander Dennis buses and Dennis Eagle dustcarts.
Dennis fire engines were noted, from their 1908 outset, for their use of a Gwynnes made centrifugal pump or 'turbine' as a water pump, rather than the piston pumps used by other makers. This was more complex to build than the long-established piston pumps, but had advantages in operation. Where water was supplied under pressure from a hydrant, rather than by suction from a pond, this additional pressure was boosted through the centrifugal pump, whereas a piston pump would have throttled it. Piston pumps also gave a pulsating outlet pressure which required an air-filled receiver to even this out.
Over 7,000 Dennis 3-Ton lorries were built for the War Department during World War I. These 3-Ton lorries could reach 55 miles per hour and climb gradients as steep as 1 in 6.Dennis were noted as specialist makers of refuse collection trucks, with compactors, bin lifters, tipper-body emptying and other specialised features for this market. The same market is now served by Dennis Eagle.