UPDATED A Thames Water engineer watched a tennis club worker pour liquid into the drain that feeds Wimbledon Park Lake, the Environment Agency has confirmed.
The club is the All England Lawn Tennis Club, better known as AELTC, which owns land bordering the lake and runs the Wimbledon Championships. It has spent the past year denying any of its staff had anything to do with pollution there, and is separately fighting residents in court over plans to expand its grounds onto the old golf course next door.
The confirmation is in a letter Putney.news obtained under freedom-of-information rules covering environmental data. It answers a request filed on 9 July, the same day as a separate request to Thames Water, which refused to release anything and which we reported on 7 August.
A Thames Water engineer, checking discoloured water and high ammonia levels near an outfall on Church Road during last year’s Championships fortnight, followed the trail onto the tennis club’s own grounds:
“During upstream investigations within the All England Lawn Tennis Club (AELTC) site, the engineer reported observing a member of staff pouring liquid into a surface water drain and food waste being present around the drain.”
His investigation was cut short by security restrictions during the tournament, the letter states.
That account is Thames Water’s, relayed by the regulator, not something an Environment Agency officer saw with their own eyes. For a year this has been residents’ word against the tennis club’s. When Putney.news put a similar account to AELTC in July, after fish died in the lake for the second July running, a spokesperson dismissed it as hearsay and promised a fuller answer on what caused the 2025 incident. It has yet to arrive. The regulator’s own file now describes, independently, the same thing residents said happened.
Nothing has followed from it. “In relation to the July 2025 incident, no enforcement action has been taken against the All England Lawn Tennis Club (AELTC) or its contractors/agents,” the letter states. Nor has anyone gone back to check: “We have not carried out any inspection at the relevant drain/outfall since the incident.” Thames Water and the tennis club set up a working group to look at the site’s drains. It met once, in September 2025, and the letter records that AELTC “had committed to resolving any issues identified.” Almost a year on, nothing has been published on what, if anything, that produced.
AELTC’s defence, unchanged since 2025, is that the drains are Thames Water’s own pipework, not the club’s own drainage. That may settle who owns the pipe. It says nothing about what a Thames Water engineer says he watched a member of the club’s own staff do to it.
The club has never had permission to put anything down that drain at all. “The AELTC site has no discharge Permits or Consents into the lake,” the letter states. Thames Water has two old overflow pipes into the same stream, at Church Road and Home Park Road, that have also never been brought under permit.
Putney.news put the eyewitness account to AELTC on 10 August and received a response after publication- see below.
This year’s problems
This year’s fish deaths are a separate story. The regulator’s account of the July 2026 kill has not changed: heat, and a bloom of a blue-green algae called Aphanizomenon, not pollution. Its officers found the water’s dissolved oxygen had crashed to about 2.2 milligrams per litre, less than a third of what a healthy lake needs to keep fish alive, and ammonia at levels high enough to irritate fish gills, though not on their own enough to kill.
Mapping the coordinates in the letter, this year’s water test was taken within about 35 to 55 metres of where the 2025 incident happened, and nobody has checked that stretch of drain this year either. That is not evidence the club is involved: dying fish and algae produce ammonia themselves as they decompose, and the regulator’s heat-and-algae finding stands on its own evidence.
AELTC’s wider expansion of the site returns to the Court of Appeal after a judge ruled the residents’ campaign group has a real case to argue that the land is protected for public use. A hearing is not expected before 2027.
Anyone who spots dead fish, distressed wildlife or unusual water at the lake can report it to the Environment Agency’s 24-hour hotline on 0800 80 70 60, or via gov.uk’s water pollution reporting service. Thames Water’s own internal review of its refusal to release this information is still open.
Update, 12 August, 2.30pm: AELTC has responded to the questions this story put to it. A spokesperson said the surface water drains crossing the wider Wimbledon catchment pass through AELTC’s land on their way to the lake.
“We support Thames Water in managing their assets by allowing access to our land for reasonable requests,” and that the club employs “consultant environmental clerks of work” to manage risk during the Championships.
They confirmed the working group with Thames Water exists and said AELTC has “a regular planned maintenance programme,” adding: “Ultimately the health of the lake will only be improved by the desilting works we have committed to as part of the benefits package linked to our planning permission for the former Wimbledon Park golf course.”
The response does not confirm or dispute the specific account of a staff member pouring liquid into the drain, does not say whether AELTC agrees no enforcement action or inspection has followed, and does not address whether the club has ever held a discharge permit for the site. This story will be updated again if AELTC addresses those three points.
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