"I've always believed that, if you can explain it so that people believe in it, they react in the right way,
Lesniak's early experience of making a big financial presentation to the board of J. Walter Thompson says it all: "I did pictures with stick men in front of a board full of creatives and I didn't realise how daring that was. Afterwards, JWT's creative director, Nick Welch, came up to me and said: 'When I saw you put up those stick men I knew we were lost.'
"From then on I always had a great relationship. They would talk to me, they enabled me to come in and understand and they were prepared to listen so you could get their buy-in to the activity. It gave me a framework in which I felt confident operating."
She is the first to acknowledge that the quality of financial management in the advertising industry has improved immeasurably in recent decades.
She also accepts that the technical accounting challenges are relatively undemanding. So why does she believe that there's a shortage of top quality finance director candidates?
"It's about having a feel for the business, to feel when something's going wrong. We've been so left-brain trained that we need to bring back some of the balance of the right brain. The really good candidates are those with personality, who have the confidence to argue and the confidence to listen."
Like many in the industry, Lesniak's career started at Andersen, the accounting firm that used to be renowned for quality and arrogance in equal measure before the Enron scandal blew the business apart. Her entry into the advertising industry came with a job at WPP Group, where she spent the next seven years, including stints at JWT and Ogilvy & Mather, before joining BBDO in 1994.
What was behind the decision to jump ship to Omnicom? "The challenge of the completely different creative entrepreneurial environment,
she responds. "After seven years in the WPP environment, which was the epitome of efficiency and success in terms of the command and control structure, I got this phone call from BBDO and it was so completely different from WPP - it had absolutely no systems, no structure, but yet this wonderful creative product and great financial performance. So I was quite intrigued."
This leads us to examine why Omnicom's businesses appear to enjoy a considerable amount of management autonomy from the centre, yet produce some of the industry's highest profit margins.
"The magic is having the confidence to trust in your management. That can only work if your management is chosen according to the correct criteria.
If you've come from a command-and-control environment, then it's very scary to be in a decentralised environment and just have to believe that they will deliver at the end of the year!"
During the past seven years BBDO has moved on a lot toward having more systems. "We take the temperature a hell of lot more often and more closely than we did,
"The reason it worked originally was that Bruce Crawford bought into the very best creative agencies that had put their houses on the line, and he didn't always buy 100 per cent. Effectively those people ran their company as if it was still theirs. Even after they had sold out, they would behave like that."
Many of those entrepreneurs have now reached retirement age and left.
Lesniak says BBDO must learn that it can't replace them but, she insists: "You have to find people who can still run the companies with that entrepreneurial passion while buying into and supporting the total network requirement."
She accepts that they are a rare breed. "But they do exist, and when you find them you have to nurture them and help them. The one thing you have to watch out for is to be sure you don't get an obedient person and it's very difficult to interview for that."
Lesniak clearly lives and breathes advertising, and may find it hard to move on as she passes the reins to Peter Walker, one of Leo Burnett's most senior executives, who joined early this year. She fits so well into the job description she uses when trying to explain what it takes to be a top-rate agency finance director: "Really good ones are those with personality and who can adapt and enjoy the business - because it's a great business.
Then, as an afterthought, she adds: "But you can't take on a depressive personality, because it's a real roller-coaster!"