The start-up, to be called Hurrell and Dawson, is expected to open for business next month. Although it begins with a blank client list, the pair expect to vie with the UK's biggest shops for business.
The move will provoke widespread surprise. Hurrell was one of the Saatchi brothers' most loyal lieutenants, having joined the Charlotte Street agency 21 years ago. More recently, as the chairman of M&C Saatchi Europe, he was tasked with building an international network.
Dawson is regarded as one of advertising's best strategic brains. His exit comes just seven months after his promotion from executive planning director to chairman at TBWA\London.
Meanwhile, it has emerged that the duo will fund the start-up from their own resources. This is bound to raise eyebrows, given the scale of their ambition.
"We are investing everything we've got," Hurrell said. "We know there are people who would be prepared to lend to us, but we plan to hold our breath until we come up for air. Having run a business for a while, I know how long it will take."
Hurrell's departure from M&C Saatchi brings down the curtain on one of advertising's most famous double acts.
He and Moray MacLennan have been the public faces of the agency for a decade. McLennan will add Hurrell's international responsibilities to his current role as the UK group chairman.
MacLennan said: "Nick has wanted to run his own business for some time and to be an entrepreneur."
Hurrell and Dawson insist they have not yet begun talks with any other agency executives or creative directors about joining them.
Hurrell said it was possible the start-up would begin life with more than one creative chief, reflecting the flatter structure and integrated approach it intended to offer.
Dawson said: "If you think about the challenges facing today's clients, you wouldn't start an agency that just offered conventional ad solutions."
Both partners got to know each other when working on the Scottish Courage business for their respective agencies. However, they are understood to have clauses in their current contracts that prevent them poaching staff or clients for a specified period.
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