Read The Times review of Apocalypse Now

In the autumn of 1970 15-year-old Sam Bottoms travelled from his home in California to the little Texan town of Archer City simply to watch The Last Picture Show (1971) being filmed. His elder brother, Timothy, was one of the stars, and this was going to be his big break. But after meeting the director, Peter Bogdanovich, the younger Bottoms suddenly found himself in the film as well, alongside his brother and the likes of Cybill Shepherd and the veteran actor Ben Johnson.

Sam Bottoms played the key role of Billy, the mute, simple-minded kid who represents sweetness and innocence in an increasingly venal world. Bogdanovich’s nostalgic portrait of Small Town, Texas in the 1950s, was a major hit. It was nominated for eight Oscars, won two and launched Bottoms’s film career. He consolidated his early break with major roles in several other Hollywood films, often playing characters, either ill-equipped for the pressures of the real world or else living in their own little universe, oblivious to reality.

He was Clint Eastwood’s ill-fated companion Jamie in the western The Outlaw Josey Wales (1976). But he is probably best known as Lance B. Johnson, the pro surfer in Francis Ford Coppola’s Apocalypse Now (1979). Lance’s presence delights Robert Duvall’s crazy Colonel Kilgore so much that he organises a military attack on the basis that there is good surfing water nearby and he famously sums up the difference between American and Vietnamese culture with the words “Charlie don’t surf”.

Lance suns himself on the patrol boat with a reflective visor, paints his face and drops acid while all hell breaks loose around him. He sums up the war as “better than Disneyland”. He is also the guy who, along with Martin Sheen, makes it all the way to Marlon Brando’s temple and survives till the end of the picture.

He later said he was surprised that he survived the protracted experience of filming in the Philippines. He was infected with hookworm during the shoot, though he was luckier than Sheen, who had a heart attack and almost died.

In 1980, the year after the film came out, Bottoms married Susan Arnold, one of the film’s editors, and they had two children before eventually deciding to get divorced. It was impossible to play the naive innocent for ever. His career stalled in the late 1980s, though he appeared in supporting roles in several recent Hollywood films, including Seabiscuit (2003) and the romantic drama Shopgirl (2005).

The third son of an art teacher, Samuel John Bottoms was born in Santa Barbara, California, in 1955. His brother Timothy was four years older and began acting as a child. Desperate to follow his brother’s example, Sam was acting in youth theatre by the time he was 10.

Bogdanovich’s adaptation of Larry McMurtry’s novel The Last Picture Show was to prove the big breakthrough for both brothers.

Ben Johnson and Cloris Leachman won Oscars for their performances, and the cast also includes Jeff Bridges and Cybill Shepherd, but many of the film’s most poignant moments centre on the character of Billy, forever sweeping away with his broom when he is not enjoying a film at the picture show.

Bottoms was reunited with Eastwood on Bronco Billy (1980) and played Cal Trask (the James Dean role) in a US mini-series of East of Eden (1981), with his brother Timothy as his father. He was one of the officers in Coppola’s military drama Gardens of Stone (1987), though he had some harsh things to say in Peter Biskind’s book Easy Riders, Raging Bulls (1998), about the man he had once regarded as a mentor, accusing him of abusing his power and refusing to share the fruits of his success.

Bottoms almost slipped from view in the 1990s, with a string of obscure films, though he was a guest star on The X-Files in 1995. However, his fortunes took a turn for the better in the new century. His later credits include Havoc (2005) and SherryBaby (2006).

In 2002 he married Laura Bickford, a successful producer whose own credits include Traffic (2000) and Che (2008). He is survived by Bickford, two daughters from his first marriage, and his brothers Timothy, Joseph and Ben, all of whom are actors.

Sam Bottoms, actor, was born on October 17, 1955. He died of a brain haemorrhage on December 16, 2008, aged 53