Is it legal to jailbreak an iPhone in the UK?

Is it legal to jailbreak an iPhone in the UK?

Added (1). I don't care about warranty (my iphone is ancient and I won't shed any tears if I wreck it). I just want to know if it is legal or illegal.

No but it will void your warranty

edit: i answered, it is not illegal to jailbreak your phone. However unlocking your phone yourself if illegal (jailbreaking and unlocking are two different things)