A few days or weeks later, a different member of the gang returns to burgle the house using the intelligence gathered by the initial doorstep trader.
Some scammers reportedly even sniff the bank notes they are paid with to judge whether they may have come from a larger wad of cash being stored somewhere in the house.
So-named because the original scammers hailed from Nottingham and would come knocking door-to-door to trade their wares, the scam has spread across the country, sparking a number of police alerts.
Forces across the country have issued warnings to vulnerable residents, especially the elderly, to be on their guard.
In some cases doorstep hawkers have forced their way inside a property after being told to go away.
Those who do pay up risk being added to a list of willing customers and are then targeted by other street sellers.