Patel, who will oversee agency operations and a portfolio of clients, will report to chief executive Jon Sharpe. She ran the M&S account from 2012 until earlier this year, helping to launch the retailer’s "Adventures in" extension of its long-running "food porn" campaign, as well as the "Leading ladies" fashion work.
M&S moved its ad business into RKCR/Y&R’s WPP sibling Grey in August, ending a 16-year relationship.
Since joining RCKR/Y&R ten years ago, Patel has led accounts including the BBC, TUI and Virgin Money. She was new-business director between 2010 and 2012.
Sharpe said: "Priya is utterly fearless and exceedingly intelligent. She is a great force of energy in the agency and is much-liked and admired by both colleagues and clients."