Reporting jointly to the worldwide chief executive officer and chairman, Bob Jeffrey, and the worldwide president, Michael Maedel, Lamb will assist both men in the running of five of JWT's global clients: Unilever Foods, Diageo, Diamond Trading Company, Shell and HSBC.
He will also pursue new international business and lead JWT's best practice for account directors to strengthen top client relationships.
"We have a significant number of multinational clients, which account for around 60 per cent of our revenue, so we're adding extra resource to this business; it's not a case of shoring up any of these clients," Lamb said.
After joining JWT as a graduate in 1984, he worked for the agency for ten years in both London and Toronto before being promoted to director in charge of Kraft and Kellogg.
In 1994, he joined Abbott Mead Vickers BBDO to run Sainsbury's and Gillette.
He returned to JWT in 1996 to run the newly acquired De Beers diamonds account, then moved to his current post in New York in 2001.