Peugeot is conducting a statutory review triggered by the expiry of the agency's three-year contract this September. It is understood to have contacted rival agencies with a view to taking part in a pitch.
Byrne has already joined the agency and replaces James Griffiths, who is leaving after two years as account director for Peugeot.
Graham Bentham, joint managing partner, said: "Peugeot is a long-standing client and I am sure that with Allan on board, we will maintain and reinforce our heritage of providing creative and innovative campaigns."
Byrne said: "My task will be to ensure that we build on our success as Peugeot's key strategic DM partner and continue to drive business forward."
In addition, the agency promoted James Farmer to senior account manager and Lindsey Thomas to account manager.
EHS Brann retained Peugeot when it was asked to repitch three years ago. It has a relationship with the client going back to 1994.
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