During another telephone conversation, Stewart, the first-class travelling salesman, outlined to a possible sponsor the commercial potential on offer in return for their backing and suggested they might fit in an appointment between his forthcoming engagements: a Concorde round-trip to New York, a brief touchdown at base in Geneva, a commitment in London and another round of business negotiations in the Asian Pacific.
He went through some of his more urgent admin before settling down to talk. Just another hour in the life of a workaholic who, at the age of 56, is now having to find time for the biggest challenge of his career.
He scarcely needs the money, the hassle, or, you would have thought, any further fulfilment. Since he retired as a racing driver with 27 grand prix wins and three world championships, Stewart has become the consummate ambassador for a range of companies. And yet, as the current Formula One challengers complete their preparations for the first race of the season, in Melbourne on Sunday, Stewart is assembling a 150-strong grand prix team and raising a budget of pounds 20m for the start of next year's world championship.
Stewart - small, trim and dapper - still looks fit enough to race a Formula One car. Driving himself to a new agenda, he contends, is "a question of time management".
"We all think we work hard, and then we realise there are crevices of time that can be used more positively. What we're doing on this car journey is a simple yet effective use of time.
"There's an elastic band which you learn to stretch and stretch, but you know when it breaks so you don't ever take it to that. As you grow older and have more experience, you are able to achieve more. You thought you were running before, but the straight becomes easier."
Formula One, however, is a ruthless, pulverising environment which usually appeals to young men and turns them old very quickly. At an age when most are contemplating retirement, Stewart is undaunted and uncompromising. "It's not a question of needing something. I don't think it's anything to do with age. I still feel very young, very motivated, I don't see it as having to justify something. I think it's there, it's a natural progression from PSR to SGP."
PSR is Paul Stewart Racing, the organisation he and his son founded to run teams in the lower formulae. They have won eight championships and always intended graduating to Formula One if the right opportunity came their way. Ford, Stewart's long-standing associates, presented that chance, offering him the position of standard bearer for the company with an exclusive five-year engine deal. Hence the birth of SGP - Stewart Grand Prix. Stewart senior is chairman, Stewart Jnr managing director.
It amounts to a huge gamble. Reputations are on the line and it is possible that Stewart, having thrived for more than two decades on the back of his racing success, could undermine all by becoming a failed team boss.
"I can't worry about that," he said, indignantly. "If that had been the case I would have retired after my first world championship or my first Formula One win. I've had my success and now I'm going to try and make a success of this - off the track as well as on the track. I think you're going to see new ground broken in the way we do business.
"Most racing teams just want to go racing. They are hard-core enthusiasts and they become businessmen as they become more successful. We feel very deeply for it, but we're not going in just through passion and wild exuberance. We're going to deliver our partners potentially more money than they're going to be spending."
Stewart pledges to the four or five partners he seeks the benefit of his contacts and leverage in the world of commerce. How the ill-starred Pacific and Simtek teams would have welcomed his clout, but then Stewart is adamant his venture will not be launched unless he meets his funding targets. I think their ambition was heartfelt, and their desire deep, but they went into it without enough money to do the job. To get the right designers, the right staff, the right equipment, the right technology.
"If we don't have that we won't go. If we're going to be five to six million pounds a year short, it categorically won't happen. I won't get into a situation where we're going to make our company bankrupt by proceeding when we shouldn't."
Stewart has already encountered the fabled reticence of British companies. "This is a British effort," he maintained. "I'm a proud Brit and an even prouder Scot, but at the moment it's proving extremely difficult to get the attention of companies here. I'm getting far better response elsewhere."
Assuming Stewart succeeds in putting together the required budget, he will still find the route to the upper echelon congested and hazardous. "That's the challenge. What did Ken Tyrrell do? What did McLaren do? What did Williams do? Benetton struggled for years and it only started to work for them when Flavio Briatore arrived.
"We're going to have our problems and I'm sure people are saying we've only seen the tip of the iceberg. I know that. But others have had to break the ground. They've done it and are duly proud of it. I'm not saying we're going to do it. I've never promised that. I do say we're going to make the very best effort."
Stewart, who always propounded the theory that even the best of drivers need five years to become champions - "Michael Schumacher has been the exception" - is setting out a similar timescale for his team.
Next year, he hopes, his cars will be midfield runners, in year two regular top 10 finishers, in year three regular points scorers, and in years four and five race winners and challengers for the championship. Stewart is scouring the market to recruit the best possible talent for his design and engineering departments, and expects to announce his drivers in the summer.
"The driver situation is very important," he said, a seemingly obvious statement yet one some team bosses are reluctant to concede. "We can't aspire to a Schumacher and at this stage, I doubt we can aspire to a David Coulthard. He's got a two-year contract with McLaren. But anyway he should be looking towards a world championship, and he can't expect to have that immediate opportunity with a brand new team. I've got no illusions about that. We would look for an experienced driver who knows how a team works and could help us in that respect and, ideally, a product of PSR."
Formula One has undergone cataclysmic changes since Stewart left the arena in 1973. He has, however, remained a regular observer and much of what he sees he likes. Some, he does not.
"I think Formula One is better than it's ever been, but the atmosphere in the paddock area is oppressive. It's not of a happy disposition. When I go to a major golf tournament, there's excitement but there's also a sense of bon viveur. There are good feelings. Formula One is probably too insular and too incestuous. Somehow or other that's got to change. I'm not saying I'm going to change that, I'm saying what I see.
"Now I'm going to live in it. I'm going to a new school. I'm walking in and seeing the class layout, and seeing the teacher's attitude, and I'm seeing the playground activity, and I'm saying `Hang on a second, why are the kids not screaming, laughing and shouting? Why is there occasionally something not going on?' It's just a little bland and I feel it could be enjoyed a little more."
As the words tumble, you have to remind yourself that school for the young Stewart was a traumatic experience. He had to fight the handicap of dyslexia and the subsequent cruelty of insensitive classmates. A determination generated then still courses through him.
"I work very hard, but I thank God that inside me I'm happy. I'm not complaining about my 18 or 19-hour days. I think `How can I be this pressed and yet still feel happy?'
"I could be saying, `I've got to do it, but give me five more years and I don't have to do it anymore.' I'm 56 years of age and I think I'll be doing this at 76, because I still feel fresh, I have the energy level, a spirit of excitement. Some of that I don't sense when I look around."
Stewart suggests Damon Hill should also relish life whether or not he drives his Williams-Renault to the world title this year. "Damon has the best chance to win the championship, but he must already be a satisfied man. He is earning a great deal of money, living in a very comfortable home, in a manner far in excess of his dreams four or five years ago. Of course he would want to win the world championship, but for his own justification? I don't know.
"I think the Williams team has the best opportunity to win. They have lost two world championships, Michael Schumacher and Benetton have won two. But you can't be as good as Williams are without cracking it.
"I believe Schumacher will win races and could win the championship. But to win it three years, back to back? Fate has a way of not letting that happen. Ferrari is the super team, with the most expensive of everything, but it's now 250 grands prix and 16 years since they achieved what they're supposed to achieve."
Stewart has an inkling Gerhard Berger, team-mate to Jean Alesi, could be the "silent strength" at Benetton and suspects Ron Dennis, attempting to restore McLaren to prominence, "has never been more driven in his life".
The portents, Stewart concludes, are encouraging. "I think it's going to be a very good season, and potentially a more open season. I think there is a sense of optimism in the whole world of Formula One. I don't know whether there's a good time or a bad time to be coming into it, and our arrival is no earth-shattering event. But I do think the time is right for us."Reuse content