Britains's biggest butterfly, the swallowtail, stages a miracle comeback

A rare butterfly is making a comeback in the UK, with numbers on the increase after a century of decline.

The swallowtail is the largest native butterfly to be found in the British Isles, with the larger females growing up to three or four inches across.

Once commonplace across the whole of Britain the swallowtail, Papilio machaon britannicus, can now only be found in the Norfolk Broads and at Wicken Fen in Cambridgeshire.

Long believed to be heading for extinction, the swallowtail is enjoying a surprise resurgence

But after 100 years of dwindling numbers, the UK's largest butterfly is making a comeback in record numbers, according to conservationists.

The success is being put down to fen management over the last 15 years which has resulted in a wider distribution of in milk parsley, a favourite food source for the swallowtail caterpillar.

This year, butterfly watchers reported seeing the distinctive yellow and black-winged insects in greater numbers than ever before.

The turnaround in fortunes began in the late 1990s when a programme of harvesting the fen and clearing scrub which had been invading the region began.

Government funding from agri-environment schemes to landowners helped finance the work.

Andrea Kelly, head of conservation at the Broads Authority, said: 'This restoration programme is a fantastic demonstration of how funding is providing magnificent wildlife results for seven million visitors who visit the Broads' magical waterland each year.'