"Policy makers, intelligence analysts and statesmen [will] find it necessary to write to each other in code. ... Once frank and private interactions among statesmen will become more diplomatic. ... This will probably lead to greater secrecy and manipulation until technology devises yet more powerful lenses to reveal even the most private state encounters."
But surely historians have always been trained not to take any documents at face value. It stretches belief to imagine that private interactions among statesmen have ever been totally frank, or that official documents have ever been completely objective. Dr Skinner advocates other forms of historical document, such as contemporary interviews with political actors, but of course these cannot be taken at face value either.
Powerful people often oscillate between discretion and indiscretion. Journalists and spies have many ways of tempting people to boast about their knowledge and influence (Vince Cable being a recent victim of such techniques - see BBC News). Given the complex psychological and political factors that trigger specific instances of disclosure, there is no reason to believe that those items disclosed are either consistently more important or consistently less important than those not disclosed. As it happens, many of the WikiLeaks disclosures are pretty banal, and some commentators have gained the impression that the life of the professional diplomat is also pretty banal, but this impression may simply be a consequence of the WikiLeaks process together with selective media reporting. Anyone who believes that WikiLeaks provides some kind of "truth" should read Slavoj Žižek Good Manners in the Age of WikiLeaks (LRB 20 January 2011).
Scandal sheets such as Private Eye have always had coded ways of disclosing information. For example, famous people are often described as "tired and emotional" (drunk) or "discussing Uganda" (having sexual intercourse).
Historians will continue to have to wade through bureaucratic self-justification, empty boasting and unsubstantiated rumour, filtered through a gauze of topical references and codes, and to try and understand the hidden power of negotiating positions that were never made explicit. (Žižek mentions a crucial meeting in Portugal in 1974.) WikiLeaks isn't going to change this very much.