Montmorency: Thief Liar Gentleman

Blurb

Montmorency is a crime novel and thriller set in Victorian era London, written by Eleanor Updale and published by Scholastic in 2003. It inaugurated the Montmorency series featuring a petty thief who turns gentleman and spy, namely Montmorency and his alter ego Scarper.
The U.S. edition was published in 2004 as Montmorency: thief, liar, gentleman? by the Scholastic imprint Orchard Books.