There are lots of variables to this question, quite often NHS surgeons find they don't have a vascular surgeon to help so have to do that work themselves, it can take twice as long as normal if there is a vascular problem and bleeding. Remember we are near the major blood vessels of the body during the surgery.

It also depends how many levels you are talking about, and how easily the surgery goes because we have nerves and blood vessels in different places, no one person is identical to the other but usually a single level takes between 1 1/2 and two hours, I have known 2 level takes six hours but quite often it's a four-hour job at the most.

Again a strange though it may seem it depends on the dexterity of the surgeon, and how used he is to doing disc replacement. I know Dr Zeegers who's done over 2000 quite often has got the job finished in about an hour, but remember that he's got a highly trained team and has been doing this since 1989.

Again it depends on how conservative the surgeon wants to be with the surrounding body, there is no fixed answer to this question I'm afraid.