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Engine house: Where Sir William and Bessie live side by side
During World War Two, Sir William Prescott and his wife Bessie were responsible for supplying north London with millions of gallons of clean water each day. This may sound somewhat far-fetched, at least until the duo’s identity is revealed – they are in fact mammoth-sized steam engines.
Completed in 1928, the Worthington Simpson triple-expansion engines were at the centre of the Kempton Park water treatment works in Middlesex, which during in its heyday in the 1960s employed 144 people and delivered 86 million gallons of water a day.
The entire site eventually switched to electric pumps, and the two steam engines were the last working survivors of their type in the UK when they retired from service in 1980. They lay derelict and abandoned for years until a group of dedicated volunteers set out to pump new life into the old machines, and the first public steaming was finally held in 2004.
Today the engine house is open to the public who come along to admire what can only be described as green giants of metal at the heart of the tall building.
Engine No 6 – also known as Sir William Prescott after the British engineer and politician – is the largest triple-expansion engine in the world. It sits alongside the equally impressive and inviting Engine No 7, also known as Bessie. Each engine is more than 60ft high and weighs 800 tonnes. The duo is a wonderful example of the level of complexity that British engineering was capable of at the time.
Nestled down below are two steam-turbine-driven pump sets designed by Frazer and Chalmers of Erith, Kent. These were installed in 1933 to meet peak loads and to cover shutdown periods of the triples. They demonstrate the staggering cost savings and advances in technology achieved within a few short years.
Elsewhere, some of the beautifully repainted doors from the six original Babcock and Wilcox boilers can be seen, as well as restored instrumentation, including a flowmeter, a CO2 indicator and a pressure-gauge panel.
To see the mighty machines at their very best, it’s worth visiting on steam days when the engines truly spring into life. The volunteer-run guided tours are also a great way to find out more about the engines that provided Londoners with clean water for more than 50 years.
The museum is always on the lookout for enthusiastic volunteers, so if you’d like to help with restoration work at Kempton please see the website for contact details.
3 things to see
- Sir William Prescott: The world’s largest fully operational triple-expansion steam engine.
- Guided tour: Hiss. Whirr. Clang. Traverse five engine levels to discover how the great machines work.
- Kew Bridge Steam Museum: Make your day complete by visiting other pumping engines in nearby Brentford.
5 Kempton engine facts
1. In 2010 the Kempton engines were awarded the IMechE’s Engineering Heritage Award for their services to London.
2. The Metropolitan Water Board designed the engines under the direction of engineer Henry Stilgoe.
3. Engines were designed to run 24/7, but in practice the runs overlapped, with each running for nine months, then off for three months.
4. Worthington Simpson built the engines at its works at Newark-on-Trent.
5. Each engine generated 1,008 hydraulic horsepower and pumped 19 million gallons a day against a 230ft head.