Four Britons, all relatives of the Oscar-nominated actress Helena Bonham Carter, were killed in a crash on a safari holiday in South Africa.

The driver of the minibus in which they were travelling lost control after a tyre punctured and it overturned, killing four passengers and leaving at least two others injured.

Marcus Egerton-Warburton, a 14-year-old Eton schoolboy, was one of the four people killed in the accident. His mother, Fiona Bonham Carter, 51, a cousin of the actress, scrambled from the wreckage with a broken collar bone while his older brother, Piers, 16, escaped with whiplash.

Fiona’s mother, Brenda Bonham Carter, 74, and step-father Francis Kirkwood, 75, also died. The fourth victim was Kay Boardman, 54, the wife of Fiona’s brother, Graham, 48, who was also in the minibus.

The crash happened on Wednesday at 4pm in a remote area six hours’ drive from Johannesburg as the group was travelling between two game reserves. The injured were taken to Johannesburg General Hospital.

A Foreign Office spokeswoman said: “We can confirm the deaths of four British nationals in a road traffic accident on August 20.

“We are still seeking clarification about the accident from the South African authorities.”

Marcus was a keen member of the Bembridge Sailing Club on the Isle of Wright. The club announced his death on its website on Thursday.

It said that Charlie — believed to be referring to the boy’s father — flew out to South Africa yesterday.

Neighbours of Ms Boardman said: “It’s terrible. Kay was a beautiful, elegant woman and they were a devoted couple.

“He had a daughter in her mid-20s, who has gone to stay with family after hearing the news.”

Rome Godwin, a friend of Ms Boardman, told the Daily Express: “They were lovely, enjoyable people. I am in complete shock. They have moved away now but spent a lot of time im South Africa.”

Friends of the dead schoolboy have set up an online memorial on Facebook, the social network website.

One stated: “Can’t put into words how much i will miss you. You are an amazing person you will never be forgotten. R.I.P marci xxx.”

Another grieving friend left the message: “I can’t believe. I just can’t believe it. One of the nicest guys in Eton. Will always miss you Markie boy. Love you forever.”

Helena Bonham Carter’s career was launched when she starred in the 1986 film A Room With A View, one of the first Merchant-Ivory films. Her partner is the film director Tim Burton and she has worked with him in a number of his films, most recently Sweeney Todd.

The 42-year-old actress is also famous for her bohemian living arrangements and unusual dress sense. She and Burton have two children and live in adjoining houses in Belsize Park, north London, with a connecting doorway because they could not get along full time in the same house.

Ms Bonham Carter’s UK agents could not be contacted for comment last night.

In November 2006, four British tourists were burnt to death when their car crashed and burst into flames on a remote road in southern Africa.

They were on holiday in Namibia when the Land Rover they were driving overturned.

Retired builder Arthur Graham, 69, and his wife Patricia, 71, from Ryde, on the Isle of Wight, were on their way to Victoria Falls with Mr Graham’s brother, Allan, 65, and his wife, Sylvia, 63, when the crash happened.

Mr and Mrs Graham had flown to Cape Town on November 3 and the family celebrated Arthur’s birthday in Hermanus before setting off on a five-week tour of Namibia.

They crossed from South Africa into Namibia on Sunday and spent two nights at a resort before heading for Keetmanshoop. The accident happened 60 miles from the city

Explore Film

• Film Reviews

• Trailers

• DVD

• London Film Festival

Editor's choice

• The 100 Best Films of the Decade
• 70 facts you didn't know about Marvel
• The 50 Biggest Movies Of 2010