An oil spill is threatening the historic Beverley Brook, which flows through Richmond Park and is at the centre of a regeneration project supported by Sir David Attenborough.

Details of the spill, which is thought to have happened upriver on Friday, first emerged when dog workers were warned not to allow their pets into the water over the weekend.

A video of the Brook was posted on Twitter by Bill Shimmers (@shimmers58).

A spokesman for the South East Rivers Trust said: "We're grateful to people for keeping a watchful eye on the river and bringing it to our attention.

"We're as concerned as the public about this incident and the affect it will have on the river network.

"We are working with local partners to find out more. We would encourage anyone who notices incidents, larger or small, to report them to the Environment Agency on 0800 80 70 60."

Friends of Richmond Park sounded the alarm on Twitter, writing: "There is an oil/chemical spill coming from upstream down the Beverley Brook and into Richmond Park, please keep your dogs out of the water."

Thames Water, which is leading a clean-up effort, told Nub News: "We're aware of an oil pollution in Beverley Brook and have been working with the Environment Agency and contractors to minimise it's spread and impact to the river.

"Our teams are currently tracing and establishing the source of the pollution, which we believe was caused by a third party, and we have deployed booms and pads to help prevent the oil further spreading in the watercourse."

One workman at the scene described the spill as 'the worst I have ever experienced'.

And an eyewitness described the smell coming from the polluted water as 'putrid'.

Beverley Brook has been the focus of a restoration project led by renowned broadcaster Sir David Attenborough and financed by the Royal Parks charity along with key partners including the South East Rivers Trust, Friends of Richmond Park and the Environment Agency.

When the restoration scheme was launched, Sir David, who is patron of the Beverley Brook Restoration Project, stressed the importance of the work, saying: "Projects like this that restore natural habitats are vital to ensure our riverside flora and fauna thrive in the future."

A Royal Parks' spokesperson, said: "The Environment Agency and Thames Water are aware of a spillage which has flowed through Beverly Brook and they have put the appropriate control measures in place.'

It said that, as yet, there are no reports of any impact to wildlife, however the situation is being monitored.

The spill is believed to have entered the water in Pyl Brook, Morden before flowing into Beverley Brook.

An Environment Agency spokesperson said: "We were informed on Sunday afternoon of oil pollution in the Beverly Brook which flows through Richmond Park.

"Our officers went onsite with Thames Water to trace the source and also assess the impact of the pollution. Thames Water have begun the clean-up operation and we will continue to monitor the situation.

"Members of the public should report pollution incidents to our free 24-hour Incident Hotline on 0800 807060."

The brook is a popular attraction in Richmond Park for visitors and photographers.

Its name is derived from the Old English for Beaver and Stream, and means a place where beavers live – though no beavers have been able to make their home there for many years, not least because of urban pollution.

The brook has previously been threatened by sewage discharges.

The pollution is linked to the Roehampton Vale Combined Sewer Overflow, which is hidden on the banks of the brook just 200 metres from the point it enters the park.