A speckled bush cricket, Leptophyes punctatissima (Orthoptera : Tettigoniidae). Called speckled (and punctatissima) because of the tiny black dots covering its green parts. The brown 'saddle' is actually the (much-reduced) wings. This is a male; in the female of this species the wings are even smaller.
In the USA, bush crickets are known as katydids.
Photo taken in Whiteknights Park, Reading University grounds, Reading, UK, on 2009-10-11.