Dog walkers and local people who visited the park on Monday, October 31, were appalled to find thousands of dead fish and raw sewage floating in the river.

The incident occurred after a six tonne valve, in a major sewer that serves Heathrow, jammed shut on Saturday, October 29, at Cranford Bridge while engineers were carrying out routine maintenance.

Engineers from Thames Water tried to reopen the valve but were unable to do so. They then returned to the site on Sunday and used hydraulic lifting equipment overnight to force open the jammed shutter, releasing it by Monday morning.

Thames Water took backed-up sewage away in tanker lorries for treatment and enlarged a contingency pipe to bypass the problematic shutter, but the volume of sewage was too high for them to be able to tanker all of it.

Chief executive from Thames Water, Martin Baggs has said the company will now meet with the Friends of the River Crane Environment (Force), London Wildlife Trust, local anglers and the Environment Agency to discuss the full extent of the damage and how to repair it.

Mr Baggs said: “The Crane has been much improved as an urban wildlife habitat and an attractive natural resource for the community in recent years mainly thanks to the hard work of local volunteers, who are understandably upset to see their river suffer major environmental damage over much of its length.

“We deeply regret this incident and we are committed to put things right over the long term.”

Fisherman Steven Heath went to visit the site at 4pm on Monday, after he heard about the incident on the radio.

The Lyncroft Gardens resident said: “The river is finished. There are dead fish floating everywhere and it really stinks."

The fish in the river died due to a lack of oxygen in the water, caused by the pollution, but an aerator was placed in the water to try to help.

The 44-year-old said: “I have been fishing there on and off since I was a boy and I was just about to start taking my boy down there, but I would not want to go near it now.

“I hope that Thames Water will be fined and they will re-stock the river, as it’s only right.”

Thames Anglers Conservancy member, Robin Vernon, of Devon Avenue said: “It will take a decade to repair all the damage done by the sewage spill. Everything in there is just dead now.”