is there supposed to be a rubber thingy in here?
(http://sharetheexperience.co.uk/Images/GTR/nut.jpg)
yes there should be a black rubber bung,i removed mine for a ram-mount to hold my sat-nav.
Part No.92066 0071 PLUG £1.45
Ta mushly
Make sure that nut is tight. In the olden days, it wasn't and was prone to fall off.