Jim is truly a very talented reader. He managed voices from all kinds of people in this book, on his own, I believe.
And his standard British accent is not as hard as London accent to interpret.
Per his official website:
A Second Guinness World Record
"In the 'Top Ten Best Selling Audio C.D's of America and Canada',
Narrator Jim Dale takes the first SIX places
with his recordings of the Harry Potter books."
(Amazon.com - August 2005)
Jim also holds a Guinness World Record for creating
"Most Character Voices in an Audio Book - 134
Harry Potter and the Order of the Phoenix"
The above record has just been broken by Jim who created 146 voices for
"Harry Potter and the Deathly Hallows"