The deliberate release of raw sewage from Heathrow Airport has caused the deaths of thousands of fish in the nearby River Crane.
Thames Water decided to release the sewage after a valve in a major sewer serving the airport became jammed on Saturday.
The company made the decision that the comfort and convenience of passengers at the busy airport took precedence over the fate of the river's fish and other wildlife.
A statement from Thames Water said, "Faced with the unpalatable choice of letting the remaining sewage back up into the airport or spill to the River Crane, we were forced to opt for the latter, resulting in sewage entering the river and damaging wildlife, which we deeply regret".
Over the weekend sewage tankers were used to remove some of the waste before it could enter the river and the faulty valve was eventually closed with the use of hydraulic equipment on Monday morning, but despite these efforts a seven-mile stretch of the River Crane has been affected with fish including pike, eel and perch amongst the victims.
The Environment Agency (EA) estimates as many as 3,000 fish have been killed and has begun an enquiry into what they consider a 'major incident'. At the same time their officers are overseeing and helping with the clean-up operation.
The EA advise that people keep themselves and their pets out of the water until the problem is fully resolved.
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