Clutch cable adjustment - sprocket end

[Creaky]

Thank you all for the fast responses and advice.

I added another dose of penetrating oil tonight and then tried the 6 sided socket and it then released!

I took off the locknut and added some light oil to the threads, replaced and carried out the adjustment using a screwdriver through the socket and then finally adjusted at the lever.

All seems fine now. Hoping to get out and try it properly on the road tomorrow.

Thanks once again. ?