Along with the rest of the Civil Service, Customs & Excise are required by Government to market test some of their activities in competition with private sector firms. As the majority of market tests are in the Outfield, Nick Storey keeps a careful eye on how they are proceeding, especially ones where he believes Collectors may be trying to fiddle the results. He also suspects some of the private sector bidders of collusion. As the results come in, it becomes plain that not just that some bids have been fiddled and there is collusion, but that someone in the Department has leaked details to some of the external competitors. Detailed analysis and Rosemary going under cover in one of the private sector bidders identifies the people doing the leaking. Then the politics takes over, of course. "Market Forces" is the twenty-second book in a series of detective stories set in HM Customs & Excise, by Richard Hernaman Allen, a former Commissioner.