Dumb question of the year as it beats me. Standard 5 speed box with original gear knob fitted (plastic variant). What holds it in place?

I have tried turning it but to no avail. Can not see any sort of locking grub screw.

Go on have good laugh I don't mind so long as someone tells me how its done!

On mine, just screwed in place...
Sounds like someone has add thread-lock to yours!

Thanks Eugene, I had started to wonder if that might be the case. Bit more force to be applied when I have a new one to put on I think.

OK so I now have new aluminium Caterham gear knob and guess what the thread is totally different to the level shaft Looks like I can re-drill and tap it no real issue. Anyone know the thread detail of a circa 93 5 speed box gear leaver shaft? Original as built and supplied by Caterham, matched to a K1.4 Supersport.

It looks to be M14 ish but I don't currently have any dies or nuts that big to check it.

Ta

The thread on my gear lever (5 speed but much later) is 3/8 UNC which is much smaller.
14mm seems a very large diameter for a steel gear lever.

Resolved. The 3/8 inc thread had a short adapter sleeve/tube fitted to the top with the wider thread at the top to take the crap plastic gear nob. It was hidden by the gater. Brut force got it undone and the new ally nob fitted straight on just like everyone else's I suspect. Quirks of a 7. Thanks for your info Duncan