Born: June 3, 1950

Died: November 4, 2015

MELISSA Mathison, who has died of cancer aged 65, got her foot in the Hollywood door when she was 12 and agreed to babysit for Francis Ford Coppola. She went on to work for him as an assistant and writer and then teamed up with Steven Spielberg and wrote the screenplay for the film that was to become the highest-grossing movie of all time.

Spielberg had been struggling for years with the idea of making an alien movie with a difference – one in which the alien is cute and lovable, gets left behind when his spaceship leaves without him, and befriends a lonely little boy. Spielberg was drawing on personal childhood memories of creating an imaginary alien friend after his parents split up.

Mathison turned his ideas into a feasible screenplay in the space of eight weeks. The end result was ET. It cost about $10million, it was released in 1982, grossed around $800million and set a record that stood until the release of Spielberg's Jurassic Park 11 years later.

Mathison and Spielberg met on the set of Spielberg's Raiders of the Lost Ark in 1980. Mathison was dating Harrison Ford, who played the protagonist Indiana Jones. They married three years later. But the marriage ended in 2004 with one of the costliest divorce settlements in Hollywood history.

Mathison had put her career on hold to bring up their two children, while Ford banked $20million from films. The divorce settlement took into account Ford's earnings from films made while they were married and was reportedly worth as much as $118million.

Melissa Marie Mathison was born in Los Angeles in 1950. She was one of five children, her father was a journalist and her mother a writer, publicist and "food entrepreneur". She grew up surrounded by eccentric and creative individuals, including Coppola, who was a decade older than her and just getting started as a film director.

She studied political science at the University of California Berkeley, but continued to babysit for Coppola and his wife Eleanor, not just at their home in Los Angeles, but on location, picking up valuable experience of the industry.

She served as an assistant on both The Godfather Part II (1974) and Coppola's Vietnam War epic Apocalypse Now (1979), on which she met Harrison Ford. He had a tiny role in the film before he was famous.

The film industry seemed in terminal decline when Coppola, Spielberg, Lucas and Scorsese came along with a string of hits which lured audiences back to the cinema. Coppola had great success with the Godfather films, but struggled to hold Apocalypse Now together during a difficult location shoot in the Philippines and a protracted editing process.

Writer Peter Biskind, in his book Easy Riders, Raging Bulls, records how Coppola was losing confidence, but that Mathison's "wide-eyed adoration" reassured him. Apocalypse Now was another hit and is now regarded as a classic.

Mathison worked as a writer for Coppola's company American Zoetrope on The Black Stallion (1979) and The Escape Artist (1982) and there was talk of Coppola leaving his wife for her, but it did not happen. Meanwhile Ford's first marriage was on the rocks and Mathison and Ford became a couple.

She visited him in Tunisia when he was shooting Raiders of the Lost Ark and got to talking with Spielberg about his alien project. She was nominated for the Oscar for best original screenplay.

Motherhood limited her writing, but she scripted the family film The Indian in the Cupboard (1995) and continued to develop her passion project, Kundun, a biographical film about the Dalai Lama. Martin Scorsese came on board as director and the film came out in 1997, but it was expensive and failed to recoup its costs. It was her last script to make it onto the screen. Recently however she was reunited with Steven Spielberg on a new version of Roald Dahl's children's book The BFG (Big Friendly Giant) and it is due out next year.

She is survived by her two children.