1811 – 1936: From Canal Reservoir to Art Deco Lido

Ruislip Lido was built in 1811 as a reservoir to supply water for the newly built Grand Junction Canal. Designed by John Rennie and William Jessop, it was later sold to the Regent's Canal and came into the ownership of the Grand Union Canal Company by amalgamation in 1929. Always popular locally for boating, fishing, and winter ice skating, the Grand Union developed the reservoir into a leisure destination with the opening of the Lido building on the northern shore in 1936.

1945 – 1978: Birth of the 12-Inch Gauge Miniature Railway

After World War II, the company sought to expand the Lido as a day-tripper attraction for Londoners. Alongside the artificial sandy beach, a 12-inch gauge miniature railway was built in 1945–1946. It originally operated with an 'Atlantic' 4-4-2 steam locomotive named 'Prince Edward', built before the war by George Flooks of Watford, running from Woody Bay Station on the southern shore along a 1,000-yard loop beside the reservoir.

With the nationalisation of the canals, responsibility for the Lido passed to Ruislip-Northwood Urban District Council (and later Hillingdon Council). The Lido featured in several famous films, including A Night to Remember (1958) and Cliff Richard's The Young Ones (1961). By 1960, Prince Edward was replaced by an American-outline petrol-electric locomotive built by Geoffrey Hunt of Bristol, followed in 1973 by the Severn-Lamb hydraulic locomotive No. 3 'Robert', styled after British Rail's mainline 'Western' class.

1979 – Present: The Ruislip Lido Railway Society Era

Following a derailment in 1978, the railway was temporarily closed. Rather than see the railway lost, Hillingdon Council funded safety improvements and appealed for volunteers to assist in running—and subsequently take over—the line. In response, the Ruislip Lido Railway Society was formed in 1979 and assumed full operation of the railway from 1980.

The volunteer Society embarked on an ambitious transformation of the railway:

• Extending the Line to Over 2 Miles (Round Trip): Starting in 1986, the original loop was extended from Wellington Junction to Eleanor's Loop, then to Haste Hill Station (1992), and finally to Willow Lawn Station (1997), creating Britain's longest 12-inch gauge railway.
• Building 'Mad Bess' & Expanding the Fleet: New bogie locomotives—Lady of the Lakes (1986), Graham Alexander (1990, converted to battery-electric in 2024), Bayhurst (2003), and John Rennie (2004)—joined the fleet, alongside No. 6 'Mad Bess', completed in 1998 in the Society's own Woody Bay workshops as a half-scale replica of the Hunslet steam locomotive Blanche.
• 2026: Welcoming No. 10 'Dougal': In 2026, the Society acquired its second steam locomotive, the 1970 Severn-Lamb 0-6-2T+T coal-fired locomotive Dougal, regauged to 12-inch gauge.