Producer Marc Samuelson has been a pillar of the British film establishment for the best part of two decades.

The acme of a solid citizen and good committee man, he’s nonetheless fond of quoting Max Bialystock from “The Producers,” who sums up the chasm between his apparent success and his actual poverty with the line, “I’m wearing a cardboard belt!”

That, however, could be about to change.

Samuelson’s career to date, from “Tom and Viv” and “Wilde” to recent exec producer credits on “Keeping Mum” and “The Libertine,” has only been a preparation for the moment in Cannes later this month when he will unveil the final cut of his $40 million Brit kid spy pic “Stormbreaker” at a private screening for its distributors.

Just getting such a movie made with a patchwork of indie financiers drew upon every ounce of his experience and relationships forged through years trudging through the indie trenches.

But if “Stormbreaker,” directed by Geoffrey Sax, turns into a hit, it could lift the company Samuelson runs with his L.A.-based brother Peter from the crowd of struggling Brit wannabes into a new league.

Adapted by writer Anthony Horowitz from the first book in his own bestselling “Alex Rider” series, the movie has the potential to become that holy grail for any indie producer — a global franchise with serious spin-off value, wholly outside the control of a major studio.

“It will allow us to run the company properly for the first time,” Samuelson says. “I have been involved in 15 films, and never made more than enough money just to be able to keep going. You only get to build a company if you can get into the franchise business.”

He has already set Horowitz to work on the screenplay for the second Rider adventure, “Point Blanc.” “We’re in serious discussions with all our existing partners and key distributors, and we’re close to saying the second film is on,” he confirms.

The list of backers for “Stormbreaker” reads like an indie braintrust — sales company Capitol Films; distribs Entertainment in the U.K., and the Weinstein Co. in North America; the Isle of Man, the U.K. Film Council, Allied Irish Bank and German fund VIP; plus pre-sales to the likes of Metropolitan in France and Telemunchen in Germany.

“This film is close to the top level of ambition for what the independent sector can put together,” Samuelson says. “But at the center, surrounded by these major partners, is still a small British independent production company.”

Without a studio to drive everything through its global machine, elder brother Peter has spearheaded worldwide vidgame and merchandising deals, while local distribs have worked with Capitol on marketing plans and promotional tie-ins.

“Stormbreaker” has absorbed most of Marc’s energies for the past two years, but over in the U.S. Peter has also produced “The Last Time” for Element Films and exec produced “The Man in the Chair.”

They have pruned their development slate to half a dozen projects, including the New Line fantasy adventure “Roofworld.”

“Things to Do Before You’re 30,” a Brit comedy shot two years ago, is finally set for U.K. release June 2. “The Gathering,” their first attempt in 2002 to make a bigger genre movie with a Horowitz script, remains unreleased four years after Harvey Weinstein bought multiple territories in Cannes.

But their big opportunity rests on the global roll-out of “Stormbreaker,” starting with that May 19 screening in Cannes. Pic opens July 21 in Blighty.

Retailers of luxury leather goods should keep a close eye on the box office. The Samuelsons might soon be shopping for new belts.