Buying Rolex at auction

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Team, never bought watches at an online auction. I know there are some horror stories that sometimes houses pass on Franken watches, watches with dubious history and sometimes out right fakes. I am looking at some lots at the upcoming Knightsbridge auction as I have friends in London who can receive the watch and bring them over to Shanghai.
Any tips on online bidding/auctions in general? I know when buying from dealers or people - "If it is too good to be true, it is." Hoping to get some watches at a decent price and sneak a steal (but cannot forget that 18% commission - ouch).
Has anyone dealt with Watches of Knightsbridge?

Thanks in advance