Thanks for your reply, I think the gaitor currently on is a replacement as there is no collar. I cannot see any plastic trim that it may be stapled to but underneath is a series of plastic pins but don't seem to connect to the top (chrome) bit so maybe its been ditched. I assume then that the top chrome part does not come off? and maybe the current gaitor has just been wedged in although it does seem quite secure. I've just had a go at prising it out and part has come away but still a little concerned at applying too much pressure incase it snaps.