It was created in 1983 when, for the first time in Britain, a public inquiry ruled that a planned development of the land could not go ahead because of its value for nature.

Its entrance, with a wooden five-bar gate flanked by hedges, is on the south of Bollo Lane, a few yards from Chiswick Park Underground station.

This was the first time anywhere in the United Kingdom that a public inquiry had ruled in favour of nature in a city, and the Gunnersbury Triangle example became a test case.

[7][9] According to the New Scientist, writing in 1985, "the celebrated Gunnersbury Triangle – an undisturbed piece of woodland surrounded by railways including the District Line ... was bought and preserved by Hounslow borough from British Rail with a GLC grant of £58 000.

[a] The GLC also gave expert ecological advice when Hounslow council contested a public inquiry to save the Triangle.

[4] The following compartments are identified in the reserve's management plan:[14] The Gunnersbury Triangle is regularly visited by school parties, totalling some 1500 students per year, mainly in the summer when they can work outside.

Following the illustrated guide, you wind among wild cherry and rowan, under archways of hazel branches to a pond where damsel-flies dance in early summer.

[17][18] On open days, staff and volunteers organise activities to enable children and adults to learn more about nature conservation in a relaxed environment.

[7] The Mayor of London's 2002 Biodiversity Strategy comments "Over the last few decades, many exciting places have been established where city people are able to enjoy the natural world, often on sites which at the outset had seemingly little to offer.

These include Camley Street Natural Park in King's Cross, Gillespie Park in Highbury, Gunnersbury Triangle in Chiswick, ..." and explains "The important message conveyed by these projects, regardless of their size, is that significant achievements for nature conservation are possible even in the most urban of settings, and often on modest budgets, provided there exists a cocktail of goodwill, optimism, commitment and professional back-up.