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

The Swallowtail, once commonplace across the whole of Britain, can now only be found in the Norfolk Broads and at Wicken Fen in Cambridgeshire.

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 an increase 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.

“More visitors are saying that they have easily spotted Swallowtails this year.”