Who has been whispering in the Cabinet Office's ear to ban the release of Lord Mountbatten's personal diaries?

The eminent and rebel historian Andrew Lownie is fighting the UK Government, and effectively the royal family, to get the release of Lord Louis Mountbatten’s diaries, so far without success.

Who has been whispering in the Cabinet Office's ear to ban the release of Lord Mountbatten's personal diaries?
The eminent and rebel historian Andrew Lownie is fighting the UK Government, and effectively the royal family, to get the release of Lord Louis Mountbatten’s diaries, so far without success.