Nine new throwbags have been installed along the River Thames between Mortlake and Barnes.

The water safety devices are being designed to buy time when someone falls into the water before the RNLI or coastguard arrived.

Cold water shock, which can cause involuntary gasping or hyperventilating, is triggered in water temperatures lower than 15 degrees C.

The average temperature of UK waters, including the Thames, is often below 12 degrees C, even in warm weather.