Paul Newman was introduced to motor racing in 1968 while filming a movie at the Indianapolis Motor Speedway, and that brief relationship blossomed into a 40-year passion for the sport that included not only co-ownership of one of the most powerful teams in US open-wheel racing, but also his own successful driving career.

Newman, the Academy Award-winning actor and world-renowned activist and humanitarian, died on Friday, aged 83, at his home in Connecticut, prompting a flood of tributes from all the worlds he inhabited.

An extremely private man, he quietly admitted that he had never paid any particular attention to motorsports until the summer of '68, when he shot scenes at the Brickyard for the film Winning. It started out merely as the latest project in which he happened to be involved but, typically, he totally immersed himself in the role, and evidently something within it rubbed off.

An early indication came when he seemed to bond with Rodger Ward, the two-time Indianapolis 500 winner who served as the film's technical director and driver of the 'camera car' for some of the on-track sequences. When Newman flew in for an exploratory visit during the spring, he stayed the night at Ward's home and, once back for the three weeks or so of shooting immediately following the 1968 500, was a guest there on more than one occasion.

While virtually all of the 'staged' on-track sequences - which were intercut with actual 1968 500 footage - were performed by a half a dozen or so current drivers, the Bob Bondurant Driving School-trained Newman elected to waive the use of a stunt double. In the footage used from the actual race, the fictitious Frank Capua is really Bobby Unser, on his way to winning the 500 but, in the majority of the close-up cockpit shots, the helmeted figure is actually Newman, matching the speed of the camera car driven by Ward.

When shooting at the track wrapped up at the beginning of July, United States Auto Club director of competition Henry Banks went over to present Newman and fellow actor Robert Wagner with honorary USAC Championship driver licences. Upon returning to the USAC office, Banks revealed, with amusement, that, at the conclusion of the brief trackside ceremony, Newman had discreetly sidled up to him to inquire what he had to do 'to do to get a real one'.

It transpired that Newman's new-found interest was more than just a whim, and it wasn't long before he began competing at Sports Car Club of America [SCCA] regional events, and doing so, without fanfare, as merely PL Newman. He entered into a long-term relationship with Connecticut neighbour Bob Sharp and raced Sharp-prepared cars for many years.

More than two decades later, when Sharp's son, Scott, qualified for his first 500 in 1994 and was being interviewed over the public address immediately thereafter, a delighted, but ever-private, Newman casually strolled into Scott's line of vision between the battery of photographers and gave the young driver a heartfelt thumbs-up.

Newman's first SCCA victory as a driver came in 1972, with a Lotus Elan at Thompson, Connecticut, not far from his home. In 1976, he won his first of four SCCA championships, this one in D-Production. A title in C-Production followed in 1979, followed by a pair in the GT-1 category in 1985 and 1986. In 1982, he beat a stellar field of professionals to win the Trans-Am race at Brainerd, and he was to win a second Trans-Am event at Lime Rock, in his home state, in 1986.

In 1977, Newman shared the fifth-place-finishing Ferrari 365 GTB4 with Elliot Forbes-Robinson and Milt Minter in the 24 Hours of Daytona and, in June 1979, he received considerable attention by teaming up with Dick Barbour and the German driver Rolf Stommelen to share the Porsche 935 which finished second in the 24 Hours of Le Mans. Less than one month later, the same trio scored another second-place finish, in the Six Hours of Watkins Glen in upstate New York.

"We were introduced driving Ferraris in 1977 at Daytona, and we developed a mutual friendship," Barbour recalled, "Paul was so passionate about driving. He told me a few times that he didn't really care for Hollywood, and that it was just a business. He really wished he had started driving earlier and made that his career. He was very consistent, never put a wheel off and was easy on the equipment."

Clearly immersed in motorsport by 1980, Newman entered into a partnership with long-time Lola distributor Haas to field a team in the Can-Am series and, in 1983, Newman/Haas Racing made its debut at Indianapolis.

But Newman already had been involved with an Indianapolis entry before that.

In 1977, he was associated with a Bill Freeman entry for which the driver was to be 'rookie' Forbes-Robinson, the very same 'EFR' with whom Newman had shared the Ferrari at Daytona that January. The programme, which had landed Caesars Palace as its sponsor, ran behind schedule, and Newman tried unsuccessfully to talk Dan Gurney into providing a car in which EFR could take his rookie test.

It was all academic. The hastily-prepared Freeman car did not arrive at the track until shortly after lunchtime on the afternoon of the final qualifying day and, with Newman looking on, not even the legendary gold-helmeted 'gunfighter' Bob Harkey had time to sort it out and get it up to qualifying speed. There would be much better days ahead.

Between 1983 and 1995, cars entered by the partnership of Newman and Carl Haas established themselves as a major force in the Indianapolis 500. While never able to pull off a win, the team did score a pair of strong second-place finishes, with Mario Andretti in 1985 and with Michael Andretti in 1991, plus a third in the hands of defending Formula One world champion Nigel Mansell in 1993.

Time and time again, it appeared that a Newman/Haas driver was destined to win the 500. In 1987, Mario Andretti led 170 of the first 177 laps from the pole, only to drop out late with an ignition problem. It was one of 13 occasions on which a Newman/Haas driver would lead the 500, and one of five in which their laps-led total would be greater than by any other driver in the race.

There are three separate instances - 1989, 1992 and 1995 - in which Michael Andretti was forced out while leading. The most devastating loss came in 1992, when he was eliminated after having led 160 of the 189 laps he completed. Between 1984 and 1995, Mario and Michael Andretti combined for an amazing 773 laps in the lead, Mansell accounting for another 34.

"It's certainly a sad day for all of us that knew Paul," Andretti Green Racing co-owner Andretti said on hearing of Newman's passing, "He was just a great guy and truly loved everything about racing. He and I shared a true passion for motorsports in general, but specifically IndyCar racing. Some of the fondest memories I have of my career are from the time I spent at Newman/Haas and I'll never forget those. Paul was one of a kind and he will be missed, for sure."

In 2004, after several years' absence, the Newman/Haas team returned, former pole winner Bruno Junqueira extending that record by leading an additional 16 laps on his way to a fifth-place finish.

It seems quite remarkable that there should have been so little turnover on the Newman/Haas driver roster at Indianapolis, Paul Tracy in 1995 being the only driver other than Mansell and the Andrettis between 1983 and 1995. In more recent years, Junqueira, Sebastien Bourdais, Justin Wilson and Graham Rahal have added their names.

"I am extremely saddened to hear about Paul's passing," Briton Wilson, who gave Newman his last win as a team owner, at Detroit's Belle Isle in August, said, "He was a great guy to be with around the track. He was one of a kind. Obviously, I am just thinking of his family and wishing them well while they are trying to deal with this. It can't be easy. He's going to be missed, not just in the motor racing world, but in every area that he participated in, in his life. He affected so many people in a positive way. I'm going to miss him and am fortunate to have known him."

"It has been a very upsetting 24 hours for the team and my family," team-mate Rahal noted, "Paul has been a huge part of both my success, as well as my father's, and he will be greatly missed. He was a tremendous man, one that everyone should model their lives after. My sincere condolences go out to the Newman family."

After a twelve-year absence, prompted by the split in US open-wheel racing, Newman personally returned to the Indianapolis 500 with his team this year after the reunification of the IndyCar and Champ Car factions.

"It's good to be back at Indianapolis," he said in May 2008, "It brings back a lot of fond memories. We've won eight championships and come in second twice at Indianapolis, but never won the 500. It's wonderful to be running against Roger [Penske] and [Bobby] Rahal, as well as Michael [Andretti] and all those guys. It's comfortable."

"We are deeply saddened by the passing of Mr Newman," a statement from Bobby Rahal's Rahal Letterman Racing read, "I had the pleasure of driving for Mr Newman in 1981 and I was richer for the experience. He was a man of class and he was also deservedly very highly regarded for his driving skills. The world is a poorer place today for his passing.

"He was a man of great courage, determination and integrity and gave a lot not only to the world of auto racing, but to the world around us. His generosity knew no bounds and his work with helping children as well as what he achieved with aiding the environment will prove to help people for many years to come."

Never losing the common touch, Newman founded the Hole in the Wall Camps charitable organisation in 1988, expanding his dream of providing a recreational and therapeutic camping experience for children facing serious illnesses and life-threatening conditions. It was one of countless philanthropic efforts.

"There are a couple of things I have great affection for," Newman said, as the Indy Racing League and Indianapolis Motor Speedway both designated the Association of Hole in the Wall Camps as a charitable partner, "One of those, as you all know, is automobile racing. The other is to care in some ways for kids who have been less fortunate than I have. And to be able to have this coming together of two organisations working together to that purpose is a home run for me. An absolute home run."

"Most of the world knew Paul as in incredible person and one of the best actors we were ever able to witness, as well as a great philanthropist," said two-time CART champion and former Indianapolis 500 winner Gil de Ferran, "But those of us in racing were very blessed to witness his passion for this sport which was very apparent. He was one of the few high-profile owners to attend tests and this made all of us see him as one of us. This is very sad news indeed and we will miss him tremendously."

They may not have seen eye-to-eye during the schism that divided US racing, but Indianapolis chief executive and IRL CEO Tony George always retained respect for Newman.

"On behalf of my mother, Mari Human George, and the entire Hulman-George family at the Indianapolis Motor Speedway and IndyCar Series, our thoughts and prayers are with the family, friends and loved ones of Paul Newman," he commented, "To all his fans world-wide and those close to him in our racing community, we share a deep sense of loss, but cherish the many fond memories we will forever carry with us."

Newman continued to race until well into his 70s, including running the Rolex 24 at Daytona as a septuagenarian. He made his last appearance at Road Atlanta, the spiritual home of the American Le Mans Series in March 2006, racing in an SCCA Regional event.

"They broke the mould when they made Paul Newman," said Tim Pappas, driver and owner of Black Swan Racing, "I had the chance to meet Paul at Daytona in 2000, and it was one of the best experiences of my life. This really is the end of an era."

The entire ALMS paddock remembered Newman on Saturday, as testing began for next weekend's Petit Le Mans - an event the great man competed in during the 2000 season - at Road Atlanta, one of Newman's favourite tracks and the backdrop for his five SCCA Nationals triumphs, in 1975, 1976, 1979, 1985 and 1986.

"I probably wouldn't be racing today if it wasn't for Paul," said Gunnar Jeannette, who first raced with Newman in 2000, "The first time I got in the car that year, he was faster than I was. Even recently, he was still incredibly quick and could get around Lime Rock better than anyone. He has been such a huge influence on my career and has been a close friend of our family for a long time."

With the recent influx of open-wheel stars into the American Le Mans Series' paddock, there were countless stories and tales to tell, most summed up in the tribute paid by former Champ Car racer, and NHR rival, Adrian Fernandez.

"There was a legend quality to Paul Newman not unlike Mario [Andretti]," the Mexican said, "He was a guy who you'd see and be around and just realise how much love and passion he had for racing.

"I always admired, as did others in the paddock, how he would often put racing before his movie career. I remember a time when he missed an important movie awards show in order to be at one of our events. He was a very sweet person to talk to about everything, not just racing. He will be sadly missed."

"It's truly a sad day," concluded ALMS series founder and former Champ Car 'constructor' Don Panoz, "Paul was one of the most iconic figures, not just in motorsports but through his life in general. He was so much more a contributor to the world than a taker. He was a dear friend and will be missed."