A combination of steel axles running in brass frames with no bearings had caused the axle holes to become oval to such an extent that the flanges were rubbing on the underside of the running plate and the valve timing had been lost. The obvious fix was to take the wheels off and fit bearings for the axles. But no, the wheels have plastic centres so any attempt to remove them would probably have damaged or destroyed them, so they had to stay on.
So what did I use to fix it? A bit of ingenuity!
It'll never be in the owner's Main Fleet again, but I know he does run it occasionally on light loads.

