Hi, Yes, I did remove a rear wheel to repair the flat.
I discovered the flat and had to detach a trailer. I then lifted the release mechanism (under the seat) so I could move the machine to flat ground.
After I replaced the wheel I re-engaged the release mechanism. However the machine would not engage either forward or reverse and the brakes did not work either.
So the problem arose not under load but with the engine turned off.
The machine can be moved easily by pushing and the brakes do not work
You are quite correct. I got there first because of responding to your questions. Of course I feel pretty stupid! There is a story of Nasruddin searching under a lamp-post for his key. Asked where he lost he points elsewhere "but there is more light here". I have now experienced being the mug in this tale. I was so sure that there must be a mechanical fault I didn't even think about the spline. Good questioning! All now well. Thank you.