A colony of grey seals in north-east England is attracting visitors to an amazing wildlife spectacle that happens once a year.

Donna Nook is a bombing range in Lincolnshire, where the UK's Royal Air Force (RAF) practice hitting targets on the beach. But every year between October and December, thousands of grey seals go there to give birth.

A viewing area has been set up by the Lincolnshire Wildlife Trust to protect the seals and the safety of visitors.