Stewart quit as Marks & Spencer's CFO on July 10 to join Tesco but a six-month notice period and the triggering of a non-compete clause in his contract meant a period of so-called "garden leave" before he could start his new job.
Separately, M&S confirmed that Carl Dawson will join the business from Tesco as IT director on September 1.
(Reporting by James Davey; editing by Neil Maidment)