Hackman, a land manager for Natural England, has laboured for 10 years to successfully re-establish cattle grazing on the two sites. Many Cotswold sites where the large blue flew in the 1930s are now dense woodland, which is useless for the butterfly.

What is the point of such elaborate reintroductions? As the sun comes out and ghostly pale chalkhill blue butterflies rise from the grass, Simcox pauses. "Isn't this wonderful?" he sighs. Managing meadows for the large blues actually helps dozens of rare species, including orchids and other insects as well as butterflies. If it goes well, this secret site will next year dance with five different species of blue butterfly. It would be pointless, Simcox agrees, if these rare butterflies had nowhere else to go, but this reintroductionfor their "drunken" flying; other butterflies fly in a more direct fashion. Also, the large blue is not actually that large – it's bigger than the other six, but not by much.

The large blue is only found in very specific locations in Somerset and Devon, including Collard Hill, which is a National Trust nature reserve and open to the public. The butterfly emerges in June and July – so if you see a blue butterfly outside these months and locations, it is another species. Patrick Kingsley

The Butterfly Isles - A Summer in Search of Our Emperors and Admirals by Patrick Barkham is published by Granta in October