Matthew Parris and Andrew Bryson, Parting Shots (Viking, 2010), 386 pages, $24.95. In 2006, Britain’s Labour government abolished a venerable institution, the art of the diplomatic dispatch. The Foreign and Commonwealth Office (FCO) in London could only acquiesce with another hasty and misguided political edict. Stung by their infelicitous commentary, they killed the message and its messenger. Blame an easily rattled Foreign Secretary in Margaret Beckett. After a document was leaked, Sir Peter Ricketts, a former permanent secretary at the Foreign Office, “halted” the tradition of ambassadors writing farewell dispatches. Governments can be badly damaged by leaks. It is one…