Damian,
If you look at the Quill Assembly part of this page from my Meddings opins/manual you will see the bottom seal part number 80.
This has, in the original, a lip on the outside of the quill.
Instructions are " Lower Quill Seal" : item no 80 is replaced simply by prising the seal housing out of the quill with the aid of two screwdrivers and inserting new assembly….."
If the seal has been replaced with a non-Meddings one then more digging required as there won't be the outside lip.
Edit: the illustration is an MB4

Edited By Robbo on 11/06/2016 09:45:22