Judging by the roles which made him one of America’s most famous movie stars, you’d be forgiven for not knowing Val Kilmer was also the youngest actor ever accepted into prestige New York drama school Juilliard. A budding playwright and Shakespearean actor when young, Kilmer’s loftier ideas about the world never quite became clear in the generally schlocky parts he became famous for. He knows this.

Val is in large part an attempt by Kilmer to correct the record, even if he’s now too frail to fully explore the side of acting which first enticed him. He handed over hundreds of hours of home movie footage to directors Leo Scott and Ting Poo, insisting the finished product play at the Cannes Film Festival.

ValWell, he got that wish. Val has been met with a positive reception and has become an unlikely hot ticket, a bit like the actor himself when he first broke into movies in the mid-1980s. From Top Gun onwards he was a celebrity and by the early-90s a household name, after winning acclaim for his portrayal of Jim Morrison in Oliver Stone’s The Doors.

But as we all know, it never quite happened for Kilmer. Top Gun made him a star but it also made people think he was unsophisticated; unlike Cruise, he would never get an Eyes Wide Shut-sized opportunity to prove them wrong. The nineties saw him star in Tombstone, True Romance, Batman Forever, Heat and The Prince of Egypt. Every performance was celebrated, and Kilmer could be proud of his work in them. But the experience of playing Batman was bruising and he struggled to sell the movie on talk shows. Kilmer’s outspoken personality and shunning of the studios saw him gain a reputation as a “difficult actor”, something which Val portrays quite movingly – yet never really takes a side on.

ValStill, it’s Kilmer’s unwillingness to bullshit which makes Val so entertaining. Never-before-seen footage from the set of the disastrous The Island of Dr Moreau will be a particular highlight for movie buffs, with some genuine laugh-out-loud moments involving a young David Thewlis and a very, very old Marlon Brando.

Kilmer’s 2015 throat cancer diagnosis hangs over the entire film, though, imbuing Val with a sad sense of dread. Combined with his gruelling but unsuccessful attempt to self-finance a Mark Twain biopic based on a hit play he toured the US with, the last decade or so has been particularly hard for Kilmer. But he’s now cancer-free and, using a clunky breathing tube, able to talk again. Val shows he still has plenty to say.