I dismantled the forks this morning after fettling the sleeve nut spanner so it finally fitted properly.
Taking everything apart was easy - more straightforward than I thought it would be.
One of the dust excluder sleeve nuts was tight but it eventually came loose with a bit of encouragement.
I followed the instructions in the original workshop manual. It all soon made sense after cross-referral with my old Haynes manual.
Within 30 minutes, I had both forks in bits and was holding a stanchion in each hand.
Both had seen better days.
The bottom of each stanchion, immersed in fork oil for 38 years, looked like new. But the top ends were decidedly rusty.
To check whether it was straight, I cautiously rolled the first stanchion across our glass-topped kitchen table.
It rolled perfectly.
I repeated the test with the second. It bobbled about, and is obviously bent.
Quite badly.
I'm going to replace the second stanchion. Or should I replace them as a pair?
I'm also going to replace both springs (which are slightly different lengths at rest), the oil seals (a sensible precaution) and rubber gaiters (perished).
Although the chrome on the original sleeve nuts is somewhat pitted, for now I am going to keep them because it will not be seen under the gaiters.
The worry about the bent stanchion now leads me to think that the top and bottom yokes might be bent.
But can't be sure until I get a new stanchion and put everything together again.
It's been a good day in terms of progress - I really feel I have achieved something.
But again it has turned out to be expensive.
I've posted more pictures below as an aide-memoire ready for fork reassembly.
Fork gaiter (wider lip goes towards top of fork)
Spring abutment (flat side towards top of fork)
Fork member (showing position of mudguard fixing)