Around 60 firefighters were called to a grass fire by The Drive in Ickenham this evening.
Eight fire engines from stations including Ruislip and Hayes fire stations were at the scene. While the fire is under control over twenty firefighters will remain at the scene for a number of hours damping down.
At the height of the fire, four hectares and six hay bales were alight.
The fire broke out next to Frays Farm Meadows, which is described as being 'one of the finest examples of rare wet grazing meadows in London and part-designated Site of Special Scientific Interest (SSSI).
Borough Commander Simon Tuhill was in charge of the incident. He said:
"Firefighters realised that the area was very important for wildlife and worked incredibly hard in extremely hot conditions to stop the fire from affecting the meadows.
"The area is home to lots of species of plants, birds and animals, including water voles, which are becoming quite rare, so it was fantastic that they were able to bring the blaze under control."
The Brigade was called at 1731 and the fire was under control at 1957.
The cause of the fire is not known at this stage but common causes of grass fires include cigarette butts, glass bottles and barbecues.
Firefighters are urging smokers to be extra careful and ensure that all cigarettes and matches are properly distinguished.
The Brigade’s tips on preventing grass fires are as follows: