just to add lilt bit more, helmet is no good without chin strap secured, if one falls from bikes ( Allah na kare ) and if helmet is not fastened by chin strap it will be off the head in first impact, if there are other impacts or obsticals they will be absorbed by the skull, not a very good idea perhaps, i owe my life to my helmet twice, once broke it while on head, both times manages to get on my feet by self, during namaz break i purchased a wire lock for my bike and helmets were at display at shop and i just asked the guy and he said Rs.800 for UNEED helmet, same one i am using, and for both you wont exceed 1k i guess in lhr.