Sir Jim Ratcliffe, the UK’s richest person with a £21bn fortune, fought a six-year battle with his neighbours, planning authorities and conservationists for permission to build his dream £6m beach house on the Solent coast in the New Forest national park.

After being rejected by the authorities five times, national park planners granted approval on the sixth attempt and the builders finally moved in last year. Just months later it was revealed that Ratcliffe, 66, one of the most vocal Brexit supporters, plans to quit the UK for Monaco to save up to £4bn in tax.

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Some neighbours close to the secluded Thorns Beach House property, which will boast a private beach, separate summer house, lake and four-car garage, said they had been won round to support Ratcliffe’s final planning application by his sheer determination to join their community.

“I saw the final plans and I liked them, they were very eco-friendly,” said one local resident, who lives further down Thorns Lane. “After six applications I thought he clearly really wants to live here, and there are worse people to live next door to than a billionaire.”

However, after learning that Ratcliffe plans to move to Monaco to save on tax she said: “If he wants to live here so much, he should actually live here. As an Englishman he should pay his taxes here.”

The local, who declined to give her name, has lived on Thorns Lane for 40 years. The area, she said, had become an enclave for celebrities and the super-rich.

Jim Wyatt, a local primary school English teacher, said the influx of very wealthy people, like Ratcliffe, had led to rising house prices, making it harder for local people and especially “commoners” (who look after the ponies on New Forest land) to stay in the New Forest.

Facebook Twitter Pinterest Aerial view of the New Forest village of Beaulieu. Photograph: David Goddard/Getty Images

“It seems a bit selfish of him to push hard for his personal dream here, and then leave the country,” Wyatt said outside the nearby East End pub, which Illsley bought to save it from closure. “We bought [our house] in the forest because of the restrictive planning. It’s hard for us to even put a garden shed up, but here you have a billionaire who has got his way after six attempts,” he said.

“If he was going to be part of the local community and contributing to the local economy and culture it might be OK, but now he’s chosen to leave that no longer holds.”

Ratcliffe, a keen sailor and adventurer who made his fortune building up petrochemicals and fracking company Ineos, bought a two-bedroom “tin cottage” at Thorns Beach for £2.5m in 2006. The house had been owned by Helen Tew, a yachtswoman who sailed across the Atlantic at the age of 89.

His first planning application, in 2011, was for a vast modernist replacement, which could be jacked up on stilts in the event of a flood. But he withdrew the plans after more than 40 formal objections. Four further applications were submitted, and the billionaire was twice turned down on appeal to the government planning inspectorate. His persistence was described as a “debilitating nuisance” by the Friends of the New Forest association.

Facebook Twitter Pinterest Jim Ratcliffe, CEO of British petrochemicals company Ineos. Photograph: Toby Melville/Reuters

Mary Montagu-Scott, daughter of the late Edward Douglas-Scott-Montagu, the third Baron Montagu of Beaulieu, had opposed the plans saying the development would “change the character of an unspoilt area”. The Montagu family owns land on all sides of Ratcliffe’s plot as part of the 700-acre Beaulieu estate.

Montagu-Scott dropped her objection to the latest application just weeks before the New Forest National Park Authority approved the plans in August 2017. Several other neighbours also wrote to the council in favour of the development.

In order to comply with planning rules, the house will consist of two connected structures – but the Ratcliffe family will only be officially allowed to sleep in one of them.

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The building project is heavily protected, with a team of six security guards working in shifts to guard the site 24 hours a day. One of the team said the building company had hired accommodation for the security team nearby.

Ratcliffe, who also owns a £77m superyacht called Hampshire II, did not respond to requests for comment on the project. The Hampshire II, which has a crew of 21 and cabins for 14 guests, is currently cruising in St Lucia.