Thanks Max,
There are several ways to fix these things but there is no way my mate is capable of fixing this sort of stuff. He has rebuilt Triumph motorbikes all his life but when it comes to improvise to get out of trouble like this he just can't do it. I know the bloke who the mower belongs to and he doesn't have a clue either and expects that things like this can be bodged up somehow with something like silicone. No bloody idea.