THIS tiny snail was the sole survivor of a huge sewage leak in the River Crane, a survey has revealed.

An estimated 10,000 fish were killed along a seven-mile stretch of the river, from Cranford to Isleworth, after a huge amount of raw sewage was released following a mechanical fault in October.

A survey carried out by Thames Water has revealed just one species survived the disaster - a member of the hydrobiidae family, commonly known as mud snails, measuring no longer than 8mm.

The creature, known as an operculum, or shutter, survived thanks to its ability to seal its shell as oxygen levels plunged.

Even the hardy midge larva, another tiny creature usually able to survive serious pollution because of its capacity to take up oxygen, had been wiped from the river.

Thames Water is working closely with the London Wildlife Trust (LWT) and the Environment Agency to restore the river, but experts have estimated this will take several years.

The survey, which is due to be repeated in the spring, suggests it may take up to a year for invertebrate levels to be restored, which is necessary for fish and birds to thrive.

Alex Robb, LWT's Richmond area manager, said oxygen levels remained low but plans were being put in place to revive the river.

"LWT is well placed to carry out wildlife monitoring and improvement works on the river," she added.

"Through the Crane Valley Project and the ongoing work of the trust at Crane Park Island we will be helping interested volunteers get involved in wildlife monitoring as soon as it is safe."

The LWT is running a regular series of conservation work days at Crane Park, in Whitton, where people can help look after the park and river.

These include:

Work days on Crane Park Island Nature Reserve - last Sunday of the month. Meet 10.30am at the shot tower

Clear scrub on the river bank, with bonfires and baked potatoes included. Tuesday, January 10, and the every first Tuesday of the month. Meet 10.30am at the shot tower

Help archaeologists investigate the site of Hounslow Gunpowder Mills at a series of mini-digs. The next session is on January 21. Meet at the shot tower. For information, email arobb@wildlondon.org.uk.