there is a nut that is a funny shape as it has the head snapped off when it is originally fitted,you need to get a centre punch and knock the nut around anti clockwise to get the igntion off it has the steering lock built into it .the original head will have been a hexagon shaped 10mm nut but as i said it snapps off when you do it up tight when its fitted from new.
adam b doc, July 2012