THERE is just the odd big bunch of delphiniums in M&C Saatchi’s London foyer these days. “Yeah, we’re very modest with our flowers now,” says David Kershaw, the ad agency’s chief executive. “These ones,” he gestures drolly at the coffee-table arrangement between the sofas in his loft-like Soho office, “aren’t even real.” Then he gives me a look. Be careful, it says.

Excessive spending on flowers was, of course, one of the things shareholders complained about the last time a Saatchi company was intertwined with the stock market. That row ended with founders Maurice and Charles leaving Saatchi & Saatchi (subsequently subsumed by the rival group Publicis) to launch a new company, M&C Saatchi, with a team of their former colleagues.

Nine years on they’re back, floating the new model on the Alternative Investment Market this week, despite a late jitter on Friday when the initial share offer was postponed, then revived two hours later. Last-minute nerves? Just a hitch over a minor legal claim, says the agency, but everyone’s getting twitchy. It was noted that Lord Saatchi and his brother, Charles, now a full-time art collector, did not even turn up to the investor roadshows last week.

Those presentations were headed by Kershaw, for many years a right-hand man to the Saatchi brothers’ previous right-hand men, and now agency leader in their place. As a man known in adland for his caustic tongue, volatile temper and steadfast loyalty to the brothers, Kershaw makes for some an interesting choice as plc chief executive designate.

Ensconced in a glass-walled interview suite adjoining the top-floor space where M&C Saatchi’s founders congregate, he brushes over the queries about what the Saatchi brothers are doing now. “I’m CEO, Maurice is executive director, Charles is non-executive. The world will carry on,” he shrugs.

As he speaks, Maurice looms large through the glass wall behind him, packing his briefcase, putting on his black suit jacket and walking out.

Is he off, too? “Maurice flits between here and Smith Square,” smiles Kershaw, explaining that Saatchi, as deputy chairman of the Conservative party, is rather busy outside the agency.

And this is where potential investors have to concentrate hard. Though the five founders of M&C Saatchi — the eponymous brothers, Kershaw, creative chief Jeremy Sinclair and new-business specialist Bill Muirhead — are billed as equal partners, some take more interest than others. Charles Saatchi, 60, doesn’t turn up (“no change there, then” as another adman joked to me); Maurice, 58, is there only occasionally; and Muirhead and Sinclair (chairman designate), both 57, are nearing retirement.

That leaves Kershaw, positively a nipper at 50, in prime position. He was once chief executive at Saatchi & Saatchi, and in effect has been lead partner since M&C Saatchi started. “But we all move together as five people,” he insists. “All the decisions are taken unanimously. It’s like a workers’ co-operative, really.” Except that, say others in London’s media village, much of the day-to-day running of the agency is now done by the next tier of management below the founders.

Baffled? So are some in the City who can’t work out why, after such a bad experience with investors last time, the Saatchis want to return to the stock market. Is it simply to cash in and say goodbye? Or just to find some way of rewarding and keeping that talented second tier? And given the lorryload of baggage being dragged to this particular table — the falling-out with Saatchi’s own shareholders last time was nothing short of spectacular — and Friday’s chaotic share launch, who will want their stock? Especially as the industry is still immured in one of the longest advertising recessions in living memory.

Kershaw, sipping Diet Coke, seems non-plussed by the fuss. “Anyone can see from the prospectus for the float that this model is so different from the old model,” he says. Last time the Saatchis were on a buying binge, this time the team has a modest plan for gradual expansion that aligns the interests of shareholders and senior executives alike. The only thing that stays the same is what the Saatchis have always been good at: relationships.

“People go on about how the assets of this business go up and down in the lifts,” says Kershaw. “Well, they don’t, they go up and down in your clients’ lifts. That relationship with the client is all you have, which is why you have to be passionate about relationships. Relationships are everything.”

The problem for outsiders is that sometimes the passion is turned on and off. Kershaw, like many of the brothers’ top team, can be ebulliently charming to some, and harshly dismissive to others. That bipolarity is a Saatchi trademark and while some find it hard to take, clients acknowledge it comes with the package.