Each engine is of a similar size to that used in
RMS Titanic and rated at about . Each could pump of water a day, to reservoirs at
Cricklewood,
Fortis Green and
Finsbury Park, for the supply of drinking water to the north, east and west of
London. Raw water was supplied to the waterworks by the
Staines and
Queen Mary Reservoirs, which stored water collected from the
River Thames. They were the last working survivors when they were finally retired from service in 1980. The engines are of an inverted vertical triple-expansion type, tall from basement to the top of the valve casings and each weighing over 800 tons. The engines are thought to be the biggest ever built in the UK. Engine No 6, also called
The Sir William Prescott, has been restored to running order and is the largest fully operational triple-expansion steam engine in the world. It may be seen in steam on various weekends throughout the year, and as a static display every Sunday between March and November. The other engine, Engine No 7, is named Bessie after Prescott's wife. The waterworks is adjacent to the
A316 Country Way, which is carried on a flyover over the grounds of the waterworks (just before it becomes the
M3 motorway at Sunbury Cross flyover), between
Sunbury-on-Thames and
Hanworth. Road access is off Snakey Lane, Hanworth. The same site also features a two-foot–gauge steam railway, the
Kempton Steam Railway, the largest steam railway offering rides to the public on selected days, in London. The steam engines now form a museum operated by Kempton Great Engines Trust, a registered charity. ==In media==