its a sad fact that alot of williams will have been clocked, there is nothing other then knowing the owner from new that i would believe, everything else in terms of history is avalible at a small cost, this will be escecialy true with the williams, the same car with the same condition might fetch £6500 with 40,000 miles and £4500 with 140,000 miles, and believe me it only takes 15-20 minutes to knock the dial back one click.