When the Ambassador Hotel was razed to the ground in November, the Hollywood landmark had not opened its doors to guests for 16 years. In its heyday, though, the 444-room hotel in the style of the Italian Renaissance played host to Hollywood. Jean Harlow danced in the great ballroom, Marilyn Monroe posed for her first modelling shots by the pool, Frank Sinatra drank and F. Scott Fitzgerald dined before famously setting fire to the bill and walking out without paying.

But by the Seventies business was dwindling. The faux palm trees taken from the set of Rudolph Valentino’s The Sheik meant little to a new generation. Howard Hughes, who had once used the Ambassador as a second home, was dead and the building had acquired another, more ghoulish claim to fame. On June 5, 1968, moments after giving a speech in the ballroom celebrating his victory in the California presidential primary election, Robert Francis Kennedy was shot.

For the next few decades the hotel paid its dues as a filming venue for pretty much any production that needed a large interior at a cut price. Pretty Woman, The Graduate and Catch Me If You Can were just a few of the films that kept the old place working.

After ten years of neglect, though, and having had the FBI and the Los Angeles Police Department use its interior for training recruits, the hotel was nothing more than a dilapidated shadow of its former self. When it was proposed that the 24 acres of prime real estate on which the Ambassador stood could be better used as the site for a school, RFK’s widow, Ethel, was one of the first to show her support for the plan. Bobby Kennedy had been a spokesman for poorer communities, fighting for equal rights and equal opportunities. He had even challenged his late brother Jack’s support for the Vietnam War, calling for peace and the return of American soldiers.

Ethel called on the veteran actor Martin Sheen to help. Having played Bobby on television, and enjoying a comeback in The West Wing, Sheen’s presidential air was perfect for the campaign to knock down the Ambassador and put the land to better use.

Two weeks before the demolition ball swung into action, though, one final film crew arrived on the site. They were there to make a small independent film, costing $10 millon, and the first to allow the Ambassador to star as itself. The film is called Bobby, and it is set in the days and hours before and after Kennedy’s assassination.

“They were literally knocking the place down around us," says Emilio Estevez, the director of the piece and Sheen’s son. “It was a great opportunity for us to get to the Ambassador in its last hours as the film is really about the ending of an era and the beginning of something quite different.”

He continues: “My father always supported the Kennedys. When I was a kid he took me to the Ambassador to pay tribute to Bobby. Hopefully the film will help to immortalise the hotel."

Bobby, due for release this year, is an ensemble piece starring such luminaries as Anthony Hopkins, Demi Moore, Ashton Kutcher, Helen Hunt, Elijah Wood, Lindsay Lohan, William H. Macy, Sharon Stone, Christian Slater, Sheen and Estevez. In classic ensemble style, it tells a variety of different stories, all taking place within the Ambassador.

The fiction will be interspersed with real footage of Bobby Kennedy, who by and large will play himself for most of the film (although Dave Fraunces, the production manager for the film, bears such a resemblance to Kennedy that he was used for some background shots of the Senator).

“But Kennedy is not the focus, he is more like the thread that holds the other stories together," says Estevez.

The weight of the film’s subject does not appear to dampen spirits on set, which is homely and relaxed. In between takes, Sharon Stone, wrapped in a full-length fur coat covering her black sequined mini skirt, has her expansive 1960s hair style primped and volumised. Lindsay Lohan charges about the set trying to find a signal for her BlackBerry, while Elijah Wood stands on a stage in a white jacket and bow-tie, waiting for his cue. At the same time William H. Macy wanders around the set in a black tuxedo sporting a tarnished Kennedy campaign badge, sharing dirty jokes with cast members.

The direction is gentle. Only on close inspection can you see Estevez huddled in a corner, his edges softened from his hell-raiser Brat Pack days, a tiny moustache on his upper lip. His presence is visible only when actors ask for direction, which is offered softly and without any sense of his being the boss. He shifts restlessly from one foot to the other as he watches Macy deliver a typically understated performance. None of it is lost on the director, or on Christian Slater, who stands by his side, giggling in admiration.

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