Phengaris arion - Large Blue 

Phengaris-arion-large-blue | PTKbutterflies
Phengaris-arion-large-blue | PTKbutterflies
Phengaris-arion-large-blue-butterfly | PTKbutterflies
Phengaris-arion-large-blue-butterfly | PTKbutterflies
Phengaris-arion-large-blue | PTKbutterflies

This species has almost legendary status in the UK, having been resurrected from extinction by brilliant research into it's environmental needs. Now re-introduced to the UK, it is thriving so far. 

The butterfly photo taken on the rock below is of the high Alpine variant, the underside shots were taken in Italy and France and all the others are from the managed site open to the public in Somerset, UK.