There is a type of customer who will break the patience of the most experienced second hand car salesman.  The first chapter in the relationship begins when the would-be buyer arrives into the showroom and is spotted by the sales agent, keen to shift some of the expensive metal, clogging up the forecourt.  After lengthy discussions, a possible vehicle for purchase is identified and the haggling gets underway. The customer digs in about the price he is prepared to pay. The salesman tries to convey such a transaction is impossible. But mindful of his sales targets and tempted by the prospect of settling a deal,…