This is taken from a book entitled "The Sacred Diary of Adrian Plass, aged 37 3/4" by Adrian Plass (the title is a lampoon of "The Secret Diary of Adrian Mole, aged 13 3/4"). I'll give the anagram in its original context, but paraphrased for reasons of (a) copyright and (b) me not being able to remember it exactly: [Gerald and Elsie are just finishing their teenage romantic relationship] As Elsie stood at the door, Gerald walked towards her and laid a hand on her shoulder. He looked into her eyes and said: "There's one thing I want you never to forget, Elsie" "What's that, Gerald?" "Elsie - I want you never to forget that `Mother In Law' is an anagram of `Woman Hitler'"
(From the "Rest" of RHF)