Guy Ritchie faced a "battle" to stop 'The Man From U.N.C.L.E.' being too funny.
The filmmaker admits he has done his best to make his retake on the classic 60s TV show serious but couldn't help but allow humour to "creep in".
He said: "At what point do you take yourself too seriously and lose a form of entertainment? It's an ongoing creative battle.
"It's really a question of keeping a muzzle on the humour. I'm always encouraged to put more humour in but I don't want to because, invariably, you lose the stakes.
"On the whole the scripts we write are written seriously and then I allow humour to creep in on the day.
"Invariably what we realise is we can make something more entertaining. Honestly, my biggest battle is to stop the cast being funnier. That is a whole wrestling match.
"The instinct is there to make it funny and I've just got to hold that back as much as I can."
'The Man From U.N.C.L.E.' follows 'Kingsman: The Secret Service' in bringing a more light-hearted tone to the spy genre and Guy insists it was a "complete coincidence", despite the other movie being helmed by his friend Matthew Vaughn.
He told SFX magazine: "It's a complete coincidence. Vaughn is my ex-partner and we know each other very well.
"We shot our films at the same time - he was in the studio next door - and I had no idea he was making the tone he was making. And he had no idea I was making the tone I was making.
"It was just one of those things. It just seemed to happen."