A bat which has a wingspan of up to 18in and was thought to be extinct in Britain has been discovered in Sussex.

The greater mouse-eared bat was found at a West Sussex site where the species was last seen before being declared extinct in 1990. It is still found in mainland Europe.

Amy Coyte, joint chief executive of the Bat Conservation Trust, said: "This is an immensely exciting discovery. We hope this means that the greater mouse-eared bat is still breeding in the UK, and that this will encourage bat workers to look out for this species."

Tony Hutson, a leading bat expert, said: "The greater mouse-eared bat is one of the largest European bats and feeds mainly on ground beetles.

"It commonly roosts in large loft spaces during the summer and tends to prefer underground sites for hibernation during the winter."

Sheila Wright of the Sussex Bat Group said members would conduct a survey in the summer to see if they could find a colony.

The Sussex hibernation site for mouse-eared bats was discovered in 1969.

No more than 30 bats were ever found and the population was reduced to one male by 1985.