I find it easier to do a role play if we start when he arrives rather than after the pleasantaries.

I suggest he knocks at the door "to see your boss". You invite him in saying your boss is running a bit late.  Does he have his letter of introduction/file so that you can "copy it for your boss" [fee].  Offer him some refreshments whilst you are waiting in your office.  Leave your "shopping" in your office, go and make the drinks, and hey presto you are away.

Best to find out in advance by email how he wants the rest to go.  Failing that if he is a fetish client he may want punishing, or if a gfe one, then he wants you to act shocked but be "secretly turned on" and then take you over the desk.

You can always wrap up if it takes a while by saying "your collegues are returning" and you need to tidy up your office.  Lol

thank you for replies - have established it is usual stuff rather than punishment (thank goodness),  he wants once i discover his naughtiness.  We've agreed to begin on his arrival (he will have to settle an outstanding invoice first!).  Really appreciate advice - will let you know how it goes x