26-04-2011, 10:01 AM
If that were mine I'd set about it with a plastic pan-scrubber (or, even better, a bit of one of the pads that go on floor-polishing machines) with linseed oil on. This makes a sort of stain out of the dirt and whatever that's on the surface which will darken the light bits. Leave it for a few hours and then wipe the excess off and then wait for it to properly dry before waxing it. You'll be surprised how well it comes up and if it still isn't up to snuff you can always take a more radical approach.
