Factual error: The police visit Richard Shaw's estate agency towards the end of the episode. The establishing background shot opposite where the estate agency allegedly is is of what was then the Cable and Wireless Building (long since bought by Vodafone). That building's real-life address is in the SE1 postcode. The problem is that the business card the police officer holds with the address has a completely different postcode.
The Lesson - S2-E3
Plot hole: At the end of the episode Trevor Speed sits with his face in his hands looking like the world has stopped turning. In fact he has just sold a worthless plot of land for £450,000. Okay, he was conned out of £150,000 of that by the grifters, but he is still £300,000 up. A grifter like him would be over the moon - he is used to taking elderly ladies for the occasional short con making him £80 or so. He's just won the lottery. He'd be happy.
Plot hole: At the end of the episode Stacie says that she has cashed the bank draft used to purchase the forged comic book artwork. Not a chance. The auctioneers establish that the artwork is a forgery within minutes of the sale going through and they would be onto their bank immediately ensuring a stop order was put on the draft. Bank cheques and drafts can be stopped after issue - it happens all time. In fact, simply by presenting the draft Stacie has opened herself up to a world of legal problems - the bank's computers are going to light up like a Christmas tree and the police will be there within minutes.
Other mistake: As we know, given the shenanigans surrounding the abortive raid on the Millennium Dome diamond exhibition in 2000, if the authorities suspected that there was to be an organised raid on the Star of Africa exhibit, it would have been replaced with a paste replica.