I wonder if there's anyone there who has been following this. Anyway, here is an update, and of course a plea for help. Having replaced the oil seal behind the clutch, and the one at the gearbox sprocket, I have put everything back together, refitted the primary chaincase cover, and today took the bike for a run, just eight miles. The leak is much, much less, but I see looking under the bike that it is still there. Please see the attached photo, taken from the right hand side side of the bike, so the front of the bike is to the right of the gearbox drain plug. Any ideas please as to where the oil is coming from? (you might remember the leak only happens when the engine is run.) Phil.