Historians and biographers should be equally mistrusting of diaries. Some diaries are a place where writers wallow in sentiment or kick around ugly ideas. Others are written for eventual publication and so are about as trustworthy as a Lib Dem manifesto. The diaries of Joe Orton, the playwright, for example, are a self-serving (and frankly boring) series of sexual adventures that cast him as an adolescent Priapus. In reality, people who met him saw a thirtysomething, giggling oddity who rubbed baby lotion into his face to make it shine.
Timmy is such a posh silly-billy he is literally incapable of judging either Larkin or Orton.
And I don't think Joe regularly put baby lotion on his face, and if he did if was just a bit of zooshing up for the cameras.
A bit like Mr Stanley's heavily Photoshopped pic here.