Jerry Gershwin
Kastner then teamed up with producer Jerry Gershwin to form Winkast Film Productions, based at Pinewood Studios in Buckinghamshire. They wound up making eleven movies together, the first of which was the highly popular Harper (1966) from a novel by Ross Macdonald and directed by Jack Smight. The screenplay was written by William Goldman who had been talking to Kastner about a film of Goldman's novel Boys and Girls Together; Goldman suggested that the Ross MacDonald Lew Archer series would make a good movie, and Kastner bought the rights. Kastner then got Goldman to write a sequel The Chill, but it was never made.
Kastner's third film was Kaleidescope (1966), made in England, directed by Smight with Warren Beatty and Susannah York. Kastner and Gershwin raised the finance independently, and sold it to a studio, Warner Bros. "That was the beginning of producers taking control creatively by self financing", said his stepson Cassian Elwes, who later became a producer himself.
Winkast then made The Bobo (1968), starring Peter Sellers and his then-wife Britt Ekland, and Sweet November (1968), with Sandy Dennis. Both were released through Warners, but Sol Madrid (1968) was released through MGM.
Sol Madrid was directed by Brian G. Hutton who helmed Kastner and Gershwin's next film, Where Eagles Dare (1968). The producer had managed to persuade Alistair MacLean to write an original screenplay as a vehicle for Richard Burton (it was later turned into a novel). The movie was a big hit and led to Kastner adapting several other MacLean stories and working with Burton a number of other times. Other MacLean adaptations included When Eight Bells Toll (1971), Fear is the Key and Breakheart Pass (1975).
Less popular was The Night of the Following Day (1969) with Marlon Brando.
Burton was meant to star in Laughter in the Dark (1969) but was fired during filming and replaced by Nicol Williamson. Kastner had involvement in Man on Horseback (1969).
In the late 1960s Kastner wanted rock star Jim Morrison to play Billy the Kid in a movie adaption of Michael McClure's The Beard.
Kastner also partnered with noted producers Alan Ladd, Jr. and Jay Kanter between 1969 and 1972, producing with them the films The Walking Stick, A Severed Head, Tam-Lin, Villain, The Nightcomers (directed by Michael Winner, with Marlon Brando), X Y & Zee (with Burton's then-wife Elizabeth Taylor) and Fear Is the Key (from a novel by Alistair MacLean).
Kastner is also famous for his film adaptations of three Raymond Chandler's novels based on the exploits of one of Chandler's most famous creations, Philip Marlowe: The Long Goodbye (1973), Farewell, My Lovely (1975) and The Big Sleep (1978). The first starred Elliot Gould and was directed by Robert Altman, with finance from United Artists. The latter two both starred Robert Mitchum as Marlowe and were financed by Lew Grade's ITC; The Big Sleep was shot in Britain under the direction of Michael Winner.
As part of the ITC deal, Kastner produced Dogpound Shuffle.
Kastner admired Altman's work on The Long Goodbye and wanted to collaborate with him in a production of 92 in the Shade by Tom McGuane, however the two men had a disagreement and the film was directed by McGuane himself. It was one of three McGuane projects produced by Kastner, the others being Ranchlo Deluxe and The Missouri Breaks. The latter starred Marlon Brando and Jack Nicholson. Kastner famously got each star to commit by lying and telling them the other one had already signed.
Around this time he also produced A Little Night Music which was a huge flop.
In a 1977 article Mario Puzo wrote about the Cannes Film Festival said that a group of producers regarded Kastner as "the greatest genius in the movie business... [he] has put together very big films, nearly all of which are flops. And yet he can get the money and stars to produce any movie he decides to. He does it with a phone, irresistible charm, and shameless chutzpah."
Colleague Jay Kanter said Kastner's reputation in Hollywood was "Some good, some bad. He was relentless in pursuing what he wanted. I mean dogged in his pursuit." He added "If Elliott believed in some material, he'd never hesitate to put his own money into buying it and hiring writers to develop a screenplay. He was passionate about what he did, and he was a terrific salesman as well."
His obituary in the Guardian stated that "Kastner was relentless in his pursuit of getting what he wanted. Mostly he wanted to entice well-known playwrights and novelists to write screenplays, or gain the rights of those works whose authors were no longer around to cajole."