The tusked mammals were wiped out in the seas around Britain when the last Ice Age ended more than 10,000 years ago. They use their distinctive whiskery snouts, packed with up to 700 hairs, to find food - typically crabs, marine worms, squids and molluscs.

There are estimated to be 250,000 in the world, most living around Canada and the Arctic. Mammal experts say they would struggle to survive if released in Britain as the climate is unsuitable.