LONDON >> Two of Britain’s boldest and wealthiest entrepreneurs are trying to break into a very tough league.

James Dyson, best known for innovative vacuum cleaners, said recently that he was preparing to introduce a new electric car and had 400 people working on the project. And Jim Ratcliffe, a billionaire petrochemical executive, is so upset about Jaguar Land Rover deciding to end production of the Defender that he said he would put a healthy slice of his fortune into producing what he calls “a spiritual successor” to the classic vehicle of explorers and safaris.

These new projects, announced within a couple weeks of each other, sent a burst of excitement through the British car industry, which has been worried about the fallout from Britain’s plans to leave the European Union trading bloc. The Daily Mail, a large circulation tabloid, even said that Dyson’s plans “would pose a threat to the Silicon Valley giant Tesla.”

But breaking into the car business is far more complex than it might appear at first glance. A new carmaker must design the vehicle and figure out how to manufacture it — and that is only the beginning. Success requires a number of to-dos: effective marketing, a dealer network and, perhaps, arranging buyer financing.

“There is a huge list,” said Peter Wells, a professor at Cardiff Business School in Wales. “That has been one of the reasons why the barriers to entry in the automotive industry have been relatively high.”

Still, Wells said that the car industry is “at a very important pivot point in its history now, where a combination of factors are radically altering what is possible.” And Dyson, 70, and Ratcliffe, 65, could be in a position to take advantage.

New technologies such as electric and autonomously driven vehicles are forcing major changes while the center of gravity in the car business is shifting toward Asia.

“There is a lot of fluidity in the entire industry space, which is what these players see,” Wells said.

In an interview at a pub called The Grenadier in London, Ratcliffe explained that terminating the much-loved Defender would create demand for a replacement because it “had left quite a hole in the marketplace.” He criticized the many SUVs still being sold as “jelly molds” that all look alike.

Ratcliffe owns two versions of the Defender — one from 1955 and a Heritage model made near the end of its production run. He said he wants to preserve the Defender’s boxy, military-style ruggedness.

Toby Ecuyer, a yacht designer, has the job of turning Ratcliffe’s ideas into drawings.

“What we are trying to design is something extremely utilitarian,” not a luxury vehicle, he said.

Ratcliffe conceded that the new vehicle will need updates to meet global safety and emission standards, including in the United States, where its sales stopped in 1997. He said he planned to make about 25,000 vehicles a year — about the number of Defenders sold in 2015, the year before its production was halted.

Jaguar Land Rover, which is owned by Tata, an India-based conglomerate, has found success with luxury models like the Range Rover. The company said in a statement that it had plans for the Defender and would pay close attention to any actions regarding its “proprietary rights.”

Ratcliffe built a $40 billion per year petrochemical empire called Ineos by buying chemical plants that other companies wanted to discard and then running them more efficiently. He said he can also find cheaper ways to operate a car company.

According to his team, for instance, European manufacturers had already expressed an interest in either building his car on contract or selling him a fully equipped plant. Either way, that would help limit upfront investment and risk. He said he did not want to put in more than 600 million pounds — less than the $1 billion analysts estimate that development and production of a new model typically costs.

Ferdinand Dudenhöffer, director of the CAR center at the University of Duisburg-Essen in Germany, said he doubted that an updated version of an old concept would have appeal beyond a dwindling group of enthusiasts. A few would buy Ratcliffe’s car, he said, but it would “become a niche which gets smaller over time.”

Dyson has been much more guarded about his plans.

“It’s not a sports car and not a very cheap car,” he told reporters at his company store on London’s bustling Oxford Street in late September. He recounted that in the 1990s he had designed a device for cleaning truck exhaust but received a cool reception from vehicle manufacturers. Instead, he focused his efforts on electric motors and batteries, hoping that one day he could step up to cars.

He has reached that point. Dyson has purchased a World War II-era airfield near his company’s headquarters in Malmesbury, in southern England, where the development work will continue. He said the new vehicle will offer a “radical” electric motor design that he said would be more efficient than those available on the market now.

Dyson has proved himself a dogged inventor, designing high-end vacuum cleaners and other products such as hair dryers. His technological savvy gives him a chance of scoring a hit in the much more complex and costly global car industry, analysts said. In 2015, he bought Sakti3, a U.S. startup that is working with solid state batteries. Dyson said he could be on track to commercializing a solid state battery, which analysts say might be more powerful and safer than the lithium ion devices now used in electric cars and cellphones. He said both the startup and his own team were working on the project.

“The edge that Dyson have if they do have an edge is to possibly be ahead of the game in solid state batteries,” said Philippe Houchois, an auto analyst at Jefferies, an investment bank.

As nascent as they are, the plans Dyson has laid out will be expensive, particularly for a medium-size company like Dyson. Dyson said he would spend 1 billion pounds on the car and another 1 billion pounds on the battery — a lot of money for a company that reported 2.5 billion pounds in revenue last year.

He may need to spend more. Tesla, for instance, has already spent about $6 billion, according to analysts’ estimates.

Dyson said he planned to develop not only a new motor but a new chassis.

“We are starting from scratch,” he said. “There isn’t one that is suitable.”

Electric cars are clearly a high-risk venture. Houchois said none of the vehicles on the market, including those made by Tesla, which recently reported disappointing production numbers on its new Model 3, are making money for their owners. Dyson might seek to bring costs down by manufacturing in Asia, where it already makes appliances.

Still, whatever his reputation, Dyson has set himself a formidable task.

“It is one thing to design and manufacture a household item,” said R.A. Farrokhnia, a professor at the business and engineering schools at Columbia University. “And quite another to prototype and then build a complex electric vehicle.”

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