Along with lots of free publicity, the episode illustrated that Ms Walker drives a hard bargain. That skill comes in handy at her new media-buying company, Walker Media. As a media buyer, she works behind the scenes, negotiating the best price for a company to place its ads in papers, magazines and on television. Launched in January 1998, Walker Media now has 230 million pounds (378.9 million euros or $339.1 million) in annual billings.

In 1998, its first year of operation, Walker Media surpassed its ambitious goal to take in over 100 million pounds of new business billings. Now Walker Media works for clients including Dixons Group PLC, Internet service provider Freeserve PLC, Marks & Spencer PLC and British Airways. She says she is bombarded by offers from people who want to buy her firm, which is 50 per cent owned by M&C Saatchi. But for the moment, she is in no hurry to return to life at a big public company.

That isn't surprising given the snarling that accompanied her departure from Zenith. Mr John Perriss, chief executive of Zenith's world-wide operations, says the agreement that was eventually settled out of court, was all a part of her initial contract. For Ms Walker, it was a "desperate attempt for [Zenith] to hold onto something they had already lost."

"They were cowards," she says scornfully. "I was one person, one individual, and they are a multinational organisation. It was pitiful."Although both Ms Walker and Mr Perriss say "the hatchet is buried," the former colleagues don't hesitate to throw a jab in the other's direction. Delicately balancing a menthol cigarette between her fingers, Ms Walker says she left Zenith because "I wanted to stop working with below-average people." Mr Perriss says Ms Walker "is very ambitious and an incredibly hard worker, but she'll never work on a big business across a wide range of clients and types of people; she's just too limited for that."

Regardless of how they have resolved the conflict, the London advertising world still remembers the battle as one of the "ugliest" in agency history, according to Mr Rupert Howell, chairman of ad agency HHCL & Parters, part of Chime Communications PLC.

When Ms Walker said she was leaving Zenith, she received numerous offers from other firms. People close to her say the most high-profile suitor was Sir Martin Sorrell, chief executive of WPP Group PLC, who at the time was setting up Mindshare, now one of the world's biggest media-buying outfits. But she turned him down. Sir Martin declines to comment on the offer to Ms Walker.

"I didn't want to recreate the same situation I had at Zenith, weighed down by bureaucracy and people who were waiting for their pensions," Ms Walker says. Sitting in her office overlooking London's Marlyebone district, she balances a high-heeled shoe on her toes, with nails painted bright pink. "I wanted to work for a private company."

So she listened with interest when she got a call from Mr Maurice Saatchi. He had been ousted from Saatchi & Saatchi after a bitter boardroom battle with institutional shareholders just two years earlier and had set up a new ad agency, closely held M&C Saatchi. "Maurice has an incredible understanding of charm," she says, "and he knows how to recognise brilliance in other people."

Mr Saatchi and Mr David Kershaw, a partner in his new firm, set about wooing Ms Walker. At first, they wanted to take a majority stake in her media venture. She refused. "I asked them: Are you kidding?" she says, laughing. "We got battered by her and her lawyers," says Mr Kershaw, remembering the long negotiations. "Finally, it was our death by lawyer and we agreed to much of what she wanted."

The two parties agreed to split everything down the middle. M&C Saatchi took a 50 per cent stake in Walker Media. Ms Walker was over eight months pregnant with her second child, but managed to meet up with Mr Saatchi and Mr Kershaw for a glass of champagne to celebrate the deal. "She was virtually on the way to the labour ward," says Mr Kershaw, "but she never let that stop her."

Ms Walker doesn't pretend to be anything but a business executive. She never considered working in advertising and says if she hadn't gone into media buying she would have become a chief executive in some other industry. Her partner at Walker Media, Mr Phil Georgiadis, is the strategic visionary in the business, a "brilliant foil" to Ms Walker's no-nonsense negotiating style, says Mr Kershaw. "To her great credit, she is very clear about her strengths, and she is also very clear about where she needs complementary skills," says Mr Kershaw. Whatever her plans, she is likely to be around for some time. "I always said I'd retire at 40," says the 47-year-old Ms Walker. "But I'm not anywhere near finished yet."