An Amazing Anagram

While waiting for the next Times crossword to appear online, I was reading an article about a book called The A-Z of Crosswords.

In the discussion, mention was made of Araucaria, one of my favourite compilers. He is known for his themed puzzles and for using very long anagrams.

They point out this one, from one of his Bah Humbug puzzles:

O hark the herald angels sing the boy’s descent which lifted up the world
which is an anagram of

While shepherds watched their flocks by night, all seated on the ground
Truly amazing! Here's a tribute the Guardian published for his 80^th birthday.