Tortoise Shield-Bug Eurygaster testudinaria
This is about 1cm long. There are other colour forms, with or without the dark markings. This is one of the Keeled Shield-bug group.
I found this one on 5 May on some sedge leaves in our garden.
Olympus EM-1 (aperture priority), Olympus 4/3 x2 TC, Olympus 4/3 50mm f2 macro,1/160 at f11 ISO 250, hand-held.
The stereos are crosseye.