London Fire Brigade

Dennis 'Big 4'

The Dennis 'Big 4' was developed in the 1930s and proved to be a popular and versatile machine that was favoured abroad as well as in Britain. Many of these vehicles remained in service up until the late 1950s.

It had a turbine pump at the rear and later versions included transverse bench seats, which made journeys far safer for the crew than the Braidwood style body. However, the crew were still exposed to the elements.

Motor vehicles were becoming faster and accidents involving members of the crew became a frequent occurrence.

The dual purpose term relates to the fact these fire engines could carry either a 50ft (15m) wheeled escape or an Ajax 40ft (12m) extension ladder.

Technical information

  • Crew: four to six firefighters
  • Equipment: delivery hoses (20 lengths), canvas hose with rubber lining, suction hoses, branches, two hook ladders, 40ft (12m) Ajax extension ladder or 50ft (15m) wheeled escape, 60 gallons of water carried in an internal tank
  • Pumping capacity: 700-1,000 gallons per minute
  • Speed: 45mph 
  • Engine: Dennis  
  • Fuel: petrol
  • Manufacturers: Dennis Brother


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