The article by Harvard historian Caroline Elkins shows that British-imperial myth-construction was integral not only to empire's functioning but its formal end as well.
The reasons for censorship are clear enough at the very end of empire. Imperial servants would not want, in the wake of victory over racist Nazi torturers and muderers, any of their own brutalities to 'muddy' the waters.
What's more interesting is the continuing reticence to release all the official papers from the colonial period. This is more puzzling, at first sight. However, a clue may lie in the resurgence of imperial thinking over the past twenty years or so. It's summed up in the phrase Tony Blair wanted to use but was advised against at the Bridgewater Hall, Manchester, in 1997, just a few miles up the road: "I'm proud of the British Empire".
The Empire was, as he and many other British and American leaders noted around that time, and especially after 9-11, an 'empire of liberty' so not really an empire at all, more like one big happy family of nations enjoying the protections and privileges of imperial rule. As a key foreign policy advisor of Blair's, Robert Cooper, noted around 1998, within the empire, peace and civilisation and order; beyond it, savagery and the laws of the jungle. At least that was the mythology being re-constructed to rationalise and justify a doctrine of post-Cold War global interventionism. Cooper urged the Anglo-Americans to lie and deceive in dealings with what he arrogantly called "pre-modern" states - i.e., those which defied the West - because they lived by the laws of the jungle. The corrollary of lying abroad, however, was deception on a mass scale at home, as Bush and Blair mis-sold the war on Iraq on the basis of an imminent military threat.
All those anti-colonial revolts, all those brutalities and counter-insurgency wars, therefore, needed to "go away", disappear. The new "empire of liberty" being constructed by the lone superpower and its chief help-mate could do without untimely and inconvenient reminders of the true character of imperial rule: in the end, empires are based less on consent than co-optation of collaborationist minorities, and principally on force for anyone who dared seriously challenge the empire.