Please can you tell me what this is and whether it's a gardeners friend or not?

Looks like the lesser stag beetle. Definite friend :)

Definitely it is, and definitely it is

Had a closer look, and I think it's female stag beetle. Lessers are matt black, and there's a hint of brown on her, plus, her mandibles are shorter. She'll nip if you put your finger in front of her, but her husband rarely will because he hasn't the movement on his great jaws.

Looks like a girl i once went out with,

Friend.

Lol Dungy

Great thanks all.