Grace's Guide is the leading source of historical information on industry and manufacturing in Britain. This web publication contains 137,406 pages of information and 221,179 images on early companies, their products and the people who designed and built them.
of Onslow Street, Guildford, Surrey
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1885 John Dennis commenced building cycles
1898 Brought his younger brother Raymond in to the business. Produced motorcycles called Speed Kings.
1895 Company founded.
1895 Built their first car.
1901 The company was registered on 1 July, and carries on the business of motor vehicle manufacturers.  John Corsey and Raymond Dennis are the founders and now the directors of the company. Planning an 8-hp car.
1904 Dennis Brothers of Guildford produced their first commercial vehicle.
1905 Advertising a worm-driven chassis suitable for a 34-seater bus body.
1905 Advert (and image) of 20 hp Laudaulette for £735. 
1907 Producing a 40 hp four-cylinder model used for charabancs.
1908 First fire engine produced.
1913 Public company formed as Dennis Brothers (1913) Ltd.
1913-1917 For a list of the models and prices of Marine Motors see the 1917 Red Book
1913-1917 For a list of the models and prices of Petrol Motor Commercial Vehicles see the 1917 Red Book
1913-1917 For a list of the models and prices of Cars see the 1917 Red Book
1913 At the Olympia show the company exhibited the 'subsidy' model based on the 3-ton commercial chassis but for the omnibus market.
1914 Patentees of the overhead worm gear.
1914 Patentees of the overhead worm gear and claim to be first concern successfully to adapt the turbine pump to fire engines.
1914 Motor and fire engine engineers. Specialities: commercial motor vehicles, pumping plants, fire engines, pleasure cars, municipal wagons. Employees 699. 
WW1 Around 7,000 of the Model A, a 3.5-ton subsidy lorry were produced in large numbers for the War Department.
1919 On 5th November, Dennis Brothers purchased the Coventry engine manufacturer White and Poppe by exchange of shares to the value of £204,365.
1931 Introduced their first diesel engine for road vehicles.
1936 Introduced a Direct Injection Diesel engine.
1937 Manufacturers of motor mowers. 
1938 Name changed.
WW2 Produced a large number of trailer fire pumps and other vehicles.
1946 Production resumed with Max and Pax 3 ton, plus a new 12 ton six-wheeler called the Jubilant.
1954 Produced a new design of 3 ton payload van with an underfloor engine called the Stork.
1957 The Max replaced by the Hefty and the Centaur by the Condor.
1961 Commercial vehicle manufacturers specialising in motor fire engines; motor coaches; omnibuses; municipal vehicles including refuse collectors, gully emptiers, cesspool emptiers, ambulances, tractors and motor lawn mowers. 1,300 employees. 
1972 Purchased by the Hestair Group. The Mercury Truck and Tractor and Mercury Airfield Equipment businesses were then sold to Marshalls (Halifax), also makers of aircraft ground support and airfield tractors