Trout have been seen spawning in a stretch of the River Wandle for the first time since the rivers fish population was decimated by pollution in 2007.

In the Carshalton arm of the river near Butter Hill, a mammoth effort by volunteers has seen the river restored to something near its former glory.

Over the past year, volunteers have been working tirelessly on the river's banks and beds to try and encourage fish to return to the area since a spill by Thames Water ravaged the fish population in 2007.

In 2007, Thames Water accidentally released 1,600 litres of sodium hypochlorite in the river, which saw more than 10,000 fish killed, and five kilometres of the river polluted.

The following year, the company was handed a £125,000 fine for undoing 20 years of river restoration work in one day.

But now trout have finally returned to lay their eggs.

Trout have been seen making a redd - a trout egg nest - which it creates by flapping its tail to clean away silt and dig a hole in the gravel before covering its eggs with stones.

A newly notched weir has allowed fish to migrate upstream and use the gravels that have been introduced as part of the river restoration works in the summer and autumn.

Erica Evans, Trustee for the Wandle Trust is delighted with the news. She said: "This is a lovely reward for all the volunteers' hard work. I would like to thank them all and the efforts they have made in restoring the river."

Trout eggs require good flows with well oxygenated, cool water for successful maturation and hatching.

Thanks to a combination of improved access for fish to new gravels and faster flows from the new installed flow deflectors, it has created an ideal habitat for the spawning fish.

The redd will allow eggs to hatch in around two months and will see tiny fish called alevins emerging and sheltering in the gaps between the pebbles below the surface of the gravel bed.