Hugh Grant was cast in 'Wonka' because he is the "funniest, most sarcastic s***" director Paul King has ever met.

The 62-year-old actor portrays a tiny green-haired Oompa Loompa in the upcoming movie - which tells the story as to how 'Charlie and the Chocolate Factory's Willy Wonka became a confectionary magnate - and the filmmaker admitted Roald Dahl's original novels didn't have much dialogue about the diminutive workers, but their songs were "incredibly sarcastic and judgemental and cruel", leading him to feel his 'Paddington 2' star was perfect for the job.

Speaking at the premiere of the trailer in London,, Paul quipped: "So I was really just thinking about that character; somebody who could be a real s***, and then — ah! Hugh!

“Because he’s the funniest, most sarcastic s*** I’ve ever met.”

Timothee Chalamet plays the title role in the film and Paul hailed the 'Call Me By Your Name' star as the "most incredible actor of his generation".

He gushed: “It was a very short list of people who could play Willy Wonka, and really, it was him.

“I really do think he’s the most incredible actor of his generation, because he’s got this incredible ability to dive very deep into his own personal emotions and convey things with the turn of an eye — he’s very, very controlled, very smart and incredibly emotionally intuitive.”

Nothing the 27-year-old actor has "some extraordinary big shoes" to fill with the role, the director is confident Timothee can "more than live up to" the previous versions of Wonka played by Gene Wilder and Johnny Depp.

He added: "I think he manages to bring that sort of mayhem and mischievousness but with a deep emotional grounding, which is really quite extraordinary.”

'Wonka' is due for release in December.