The Environment Agency (EA) was told that the Thames spill stretched from Preachers Lane to the Ice rink. Another passerby said it stretched all the way up to railway bridge.

EA spokesman Andrew Walker said: “Our officers are onsite and are currently investigating the cause and potential impact of the oil. We have not received any reports of fish in distress or environmental impact.”

However, the Agency could not immediately say how far the slick stretched or what caused it.

Concerned resident Sylvia Barker called it a 'thoughtless act' and said the slick was still visible by the afternoon. She explained: "There is an oily smell too. It indicates the lack of care for our historic river. We should be the custodians of the wildlife, not polluters of this unique stretch of river.

"Since the Thames Path has been tarmacked, there's been an increase in dumping rubbish."