Clouded-bordered Brindle.
(Apamea crenata)

This Clouded-bordered Brindle moth is quite difficult to see camouflaged against the stone.

Information:
These moths with a Fore-wing length of 18-22mm can be seen flying May-July in grassy places, open areas or rides in the woods as well as gardens. They are quite common and are distributed over just about the whole of Britain.