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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, as well as lorries and light armoured vehicles for the War Office.
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 Resumes bus production with the rear-engined Dominator chassis. Also supplied the rugged, front-engined Jubilant to Hong Kong before a three-axle version of the Dominator emerged as the Dragon and Condor models, designed to cope with extreme peak loadings of up to 172 passengers
1990 Dennis opened a new factory at Slyfield on the outskirts of Guildford to replace its ageing manufacturing plant.
By 1992 Trinity Holdings had acquired Reliance-Mercury, maker of airport tractors.
1997 Trinity Holdings planned to rename itself Dennis Group
1998 Dennis Group's products included buses, coaches, airport vehicles, dustcarts, fire engines. It withdrew from its loss-making Malaysian joint venture in buses
2007 The last fire engine was built at Slyfield; the site continued to be the centre of bus chassis manufacturing for Alexander Dennis.