Replacement Electric Aerial Mast

[JQ]

Dear All

The electric aerial on my Mk2 has never worked, so I have replaced it with a second hand unit from Ebay. Unfortunately, the aerial mast of the replacement unit is bent and so only rises about half way. Rather than sending it back the simplest solution would be to re-use the perfectly good aerial mast from the broken unit, however, I cannot work out how to remove the mast. I've completely taken the broken unit to pieces but still can't work it out.

So, please can someone tell me how to remove and then install a replacment mast for an electric aerial on a Mk2.

Many thanks