The biggest reintroduction to date of the large blue has led to the rare butterfly flying on a Cotswold hillside where it has not been seen for 150 years.

About 750 butterflies emerged on to Rodborough Common in Gloucestershire this summer after 1,100 larvae were released last autumn following five years of innovative grassland management to create optimum habitat.

The globally endangered butterfly now flies in greater number in Britain than anywhere else in the world, four decades after it became extinct in the country.