This is probably our commonest bush-cricket, the Speckled Bush-cricket Leptophyes punctatissima is a small green cricket with a brown stripe down its back (admittedly it’s not very prominent on this particular specimen) and is covered in tiny black speckles. Crickets are easily distinguished from grasshoppers by their long antennae which can be easily twice as long as the body. In comparison grasshoppers have rather short antennae.
The broad, upturned, scythe-like ovipositor at the rear indicates this is a female. She uses this to cut into plant stems or tree bark to lay her eggs where they will over winter. The nymphs will emerge in May/June and will mature as adults by mid August. Depending on the weather adults like this can still be found until late November.
It’s mainly confined to well-vegetated areas of Southern England and Wales such as woodland margins, hedges, parks and gardens.
I often discover these well-camouflaged insects perched motionless amongst the bramble Rubus fruticosus in my garden, although often as not it’s usually the tiny nymphs I find in mid Summer rather than the full-grown adults. They sit still to avoid predators and are most active in the evening or at night.
A good resource to UK Orthoptera and Allied Insects can be found at: www.orthoptera.org.uk