Earlier this month, he played a key role in one of the biggest ad-industry dramas of the decade: the move by Chrysler Group of DaimlerChrysler AG to consolidate its $2.3 billion marketing and advertising budget at Omnicom's BBDO Worldwide.

Mr Wren describes Chrysler's decision this past summer to save money by eliminating its other advertising agency, True North Communications' FCB Detroit, as "a surprise." Though he doesn't normally participate in ad agency pitches to clients, Mr Wren began paying regular visits to Chrysler's top marketing execs in Detroit, in what he modestly describes as mostly a "a show of support."

After the advertising heads at Omnicom agency BBDO made the case that they could deliver the best TV spots and print ads for Chrysler, Mr Wren chimed in to support BBDO's promise to eliminate a lot of back-office staff, allowing Chrysler to save more than $50 million.

The potential for that enormous savings turned out to be a big factor in BBDO's ultimate success in winning the Chrysler business. Chrysler senior marketing executive Arthur "Bud" Liebler says Mr Wren is "a quick study, and smart as hell." Mr Liebler adds that Omnicom "broke the paradigm" in the relationship between ad agencies and their clients by agreeing to create a stand-alone business unit, called PentaMark, to cater to the Chrysler business.

Mr Wren contends he was merely the "coach of the team, but not on the pitching mound." He says he had backed BBDO when it made the same pitch to Chrysler three years earlier, when he was in charge of Omnicom's Diversified Agency Services unit, though Chrysler didn't go for it at the time.

The father of two - a 13-year-old boy and an 11-year-old girl - waves his arms to and fro to punctuate his points about how Omnicom is a leader in public relations and advertising. Mr Wren isn't a traditional advertising guy, however. He comes from the world of so-called marketing services, which is becoming increasingly important in the advertising industry.

Marketing services, sometimes known as "below-the-line" advertising, represented a big portion of Omnicom's $5.13 billion in revenue in 1999. It generally encompasses public relations, sales promotions and other services that aren't part of the traditional advertising budget.

Mr Wren's roots in this backwater segment of the ad industry have been critical because Wall Street analysts now view marketing services as a reliable and consistent provider of revenue. Thanks to its strong diversification in a number of marketing services, Omnicom has become "the crown jewel" of the advertising industry, says Michael Russell, an analyst at Morgan Stanley Dean Witter in New York. "It's what other companies try to emulate the most."

Mr Wren has also had a great deal of luck in navigating the choppy waters of online consulting. Omnicom burst into the online world in 1996, well ahead of many of its rival advertising holding companies.

He has recently taken some chips off the table - at exactly the right time. For example, at Mr Wren's urging, Omnicom in early February sold more than four million shares of Razorfish Inc., a New York online consulting firm. The timing now looks prescient because shares of Razorfish subsequently dropped sharply along with other dotcom stocks.

Hustling through the streets of midtown Manhattan on his way to a sushi lunch with an online consulting executive, Mr Wren says he remains committed to the Internet as a sector but believes that only the dotcom companies that have been managed conservatively will survive. "We thought Wall Street looked insane and we sold our shares a month before this whole thing happened," he says.

These days, Wall Street is closely watching Mr Wren's dabbling in the world of health care and prescription drug marketing, which are a growing presence at Omnicom.

And some in the ad world say it's too early to give Mr Wren a final grade. Omnicom created a stir in ad circles by agreeing to hire the top brains from FCB Detroit to run the show at its new Chrysler unit. Some agencies think this gave Omnicom an unfair advantage. For his part, Mr Wren isn't apologetic. He says Chrysler asked for the unusual arrangement - and like any savvy businessman, he promised to deliver.

The Wall Street Journal