Richmond Park MP Sarah Olney will join swimmers in testing the quality of the River Thames at Ham this morning.

She’ll be one of thousands of people across the country taking part in a nationwide WaterBlitz.

Participants will test nitrate and phosphate levels to see how clean wild swimming spots really are.

The stretch of the Thames between Ham and Kingston became London’s first official water bathing site in May.

But it had to close to swimmers earlier this month after Blue Algae was found in the water.