The problem seems to be that the 'dirt' contains quite a lot of varnish from the floor, ingrained in the fabric, so even powerful washing liquids don't really seem to do the job. (Guess I could try Decon-90 from here in the lab, but I doubt I'd have any shoes left afterwards!) Dry cleaning would seem to be the best bet, but it would probably cost more than the shoes :-D
A.[/i]