We wrote Funny Bones with four actors in mind: Jerry Lewis, Leslie Caron, George Carl and Freddie Davies. As hardly ever happens, none of them died, and they all said yes.

I first met Jerry in Las Vegas, where we rehearsed. Walking through the crowded gambling floor of a Vegas casino with Jerry, the reactions ranged from hysteria to the shock that comes with seeing a ghost. He’s alive! Very much alive. (In fact, he was a very sprightly 69.)

From the outset, he was generous. There was only one alarm bell: he made a show of presenting me with a signed copy of his book, The Total Film-Maker. It threw me, humbled me. It reminded me I was directing a director. Was the book an instruction manual on how I should proceed? I kept expecting him to be difficult; to pull rank. He never did.

If he was ever difficult, it was in ways that never bled on to the set. No room at Blackpool’s Imperial hotel was big enough for him. In the end, it was one room for him and one for his belongings. Locks had to be changed. And I had to hide the fact that I had the biggest room, the Gigi suite – something I also had to hide from Leslie Caron for obvious reasons to anybody familiar with her filmography.

But he embraced it all. The fish, the chips – all of it. The world of my home town, Blackpool, as it appeared in my childhood.

The film is full of non-professional actors, from many different walks of life. The crew called the film “the mad, sad, uninsurable world of Peter Chelsom”. In particular, there were a lot of comedians. For me, there’s a very thin line between a talent for being funny and being a great actor. Jerry Lewis epitomised that. And that’s the thing about him – he really was a fine actor. He played it very truthfully. He understood the zone he was in: real characters in absurd situations. In Funny Bones, there’s comedy and there’s acting, but there’s no “comedy acting”. You don’t act absurd; it’s a by-product. He got that.

There is a scene where he visits his son (Oliver Platt) in his dressing room before going on to stage. He asked me how I saw it. I told him I just wanted him to “own” the room, to stay loose. I didn’t want to give him moves. I was rolling two cameras, and I would catch whatever he wanted to do – I knew he would direct himself. He knew what worked. I just wanted to watch. Take one is in the movie.

He told me he loved what the film had to say, about comedy, about our lives. He related to the polarity, the limits, the dark side of it all: this was a film where a comedian (Lee Evans) is fuelled by applause to almost murder someone on stage. Jerry embodied the term “funny bones”: a way of differentiating between comedians who tell funny and those who are funny. He was definitive casting.

I had been obsessed with the essence of comedy from the age of seven. Jerry used to ask me: “How do you know all this without coming from a show business family?” Then one day, I pointed out Butlin’s in the distance. “You see Butlin’s, Jerry? My grandmother won the glamorous grandmother competition there five years in a row. And I’ve got all the cups to prove it.” He smiled, spread his arms and said: “So you do come from a show business family!”