TV presenter Steve Backshall has described a 10-hour discharge of untreated waste into the River Thames near Marlow as ‘heartbreaking’ and urged locals to ‘stay educated and stay angry’.

Thames Water, which was handed a £104 million fine for failing to manage sewage spills in August, discharged waste in Little Marlow for 10 hours on Monday, September 23, after some parts of the UK saw a month’s worth of rainfall in just 24 hours.

It’s the latest in a series of incidents that spurred Backshall to test samples of the river near his Thames-side home for bacteria back in April – uncovering “horrifying” amounts of E. Coli and norovirus.

The water company has previously attributed such prolonged discharges to “excessively heavy” rain causing river and groundwater levels to rise – but to environmental campaigners like the Deadly 60 presenter, such explanations are too little too late.

In a video uploaded to his social media on Tuesday, Backshall described the most recent discharge as “a bleak day for our waterways”.

Adding: “Just upstream of here, we had 10 hours of sewage pouring into the Thames yesterday, which is heartbreaking because finally, after months, our otters are back – they were here on the deck last night. Kingfishers are back too, as well as the wild swimmers.

“All I can say is, if you are a river user, stay informed. Get a hold of those numbers and act accordingly. We need to stay educated, use our voices and stay angry (about) the state of our waterways.”

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He also praised the secretary of state for the environment Steve Reed for “talking some big things about the changes that are to come” but acknowledged that they “would take time” – making speaking out about the sewage dumping each time it occurs even more imperative.

Mr Reed has said he wants to “attract billions in private sector investment” into the water industry and upgrade England and Wales’ water infrastructure, with a special measures bill introduced to parliament on September 4 handing new powers to Ofwat and the Environment Agency to take action on companies damaging the environment and failing customers.

Joy Morrissey, Conservative MP for Beaconsfield, also said she was “deeply concerned” to hear about the spill on Monday, telling constituents that she had contacted Thames Water to “request an urgent meeting”.

She added: “Whilst the upgrade to the Little Marlow Sewage Treatment Works is welcome, until it is completed, Thames Water needs to demonstrate they are doing all they can to prevent discharges.”