Andrew Barclay was the major British builder of Fireless locomotives and during the years 1910-1961 produced 114 of these machines, more than all the other British builders put together.

The first trial of a wholly fireless loco took place in New York during October 1873. This and subsequent experiments in Europe concerned the use of the type on short distance suburban workings, underground lines and tramways. But it was the German company, Orenstein and Koppel who first produced the type of fireless locomotive we know today. They recognised that many customers could make use of a steam locomotive which did not carry with it fire risk or clouds of smoke and coal dust. For instance, munitions factories, paper mills, oil refineries and foodstuff producers. Fireless locos were also popular with power stations and chemical plants where they could be charged from an already abundant steam supply to provide a cheap form of motive power.

It was also Orenstein and Koppel who introduced the fireless principle to Great Britain when in 1907 their Drewitz plant built an 0-4-0 for Empire Paper Mills, Greenhithe, Kent. The first successful British machine did not come until 1913 when Andrew Barclay delivered No. 1207 to the Admiralty Explosives Depot, Bedenham, Hampshire. The Great War saw a rush in the construction of these engines for use in the armaments industry, but thereafter production fell off to a handful every year until 1961 when 163 units had been built by ten manufacturers.

Mechanically, fireless locomotives are much the same as any other steam engine, but instead of having a boiler, a large, well insulated, reservoir is mounted on the mainframes. This is charged with steam from an external source to about 180 psi (12.4 bar) and the loco is capable of useful work until the pressure drops to 30 - 40 psi (2.1 - 2.8 bar). One charge can last for several hours, depending on the amount of work to be done. An important thermodynamic principle enables the fireless locomotive to make the most of its charge of steam. As the pressure drops the hot water remaining boils again at the lower pressure due to the temperature having remained fairly constant, thus producing more steam for further work. Unfortunately the process is not continuous because of heat loss and also the drop in water level as it is turned to steam. Once the reservoir is warm however, recharging is quite quick.

The Quainton Railway Centre was the first preservation organisation to restore a fireless locomotive to working order. Instead of a factory boiler, another conventional steam loco is used to charge the reservoir. The engine to be charged is coupled up to a locomotive which has been fitted with the necessary equipment for the operation, steam being fed into the fireless machine's reservoir via a high pressure flexible and non-return valve.

Examples at Quainton