When creating the villain for Paddington 2, the film-makers had to write a very delicate letter to Hugh Grant, explaining why they thought he would be perfect to play a washed-up, self-important actor.

Indeed, they were so keen on the star of Four Weddings And A Funeral (1994) and Bridget Jones's Diary (2001) that they called the character Hugh throughout the writing process.

"We always wanted the villain to be him," says writer-director Paul King to media at The Shard in London last month, "and we called our character Hugh Grant for about six months because you have a voice in your head when you are writing.

"And then I had to write this very awkward letter going, 'Dear Mr. Grant, we have written this character in Paddington 2 who is a washed-up, vain, self-important, probably not very good actor whose best days are behind him. And we immediately thought of you.'"

King, who also wrote and directed the first Paddington film (2014), says that though he always found Grant very amusing on screen, he had never met him and had no idea how he would respond.

He says: "As it happens, Hugh doesn't take himself seriously at all. In fact, he has a very healthy disdain for the entire acting profession and he has lots of funny anecdotes from his days in repertory theatre, with various, ghastly old loves."

Grant shines in the role of Phoenix Buchanan, who emerges as the nemesis to the film's titular hero, a small brown bear from Peru.

As with the first movie, the film is a live-action piece with a CGI bear, voiced once more by James Bond star Ben Whishaw. Paddington 2 opens here tomorrow.

The bear, with his old hat, battered suitcase, duffle coat and a penchant for marmalade sandwiches, is a classic character from English children's literature.

Grant says he quickly downloaded it after he was offered the role and adds that he admired it immensely. "It's quite a difficult thing to make children's films without going sentimental or yucky, and it was a very clever trick that Paul King brought off with that film," says the actor who rummaged through memories from his early career on stage when putting his criminal character together.

"I spent a lot of the early part of my career in the 1980s doing plays with memorable theatrical types. I pillaged them all for this character, for the almost unendurable, overweening vanity of the man. He can't see beyond his own beauty and talent, and that makes him do things that I'm sure he's ashamed of."

The role of an archvillain is absolutely vital to the success of a children's film and much of the fanfare around the first Paddington movie, which took more than US$260 million (S$350 million) at the worldwide box office, centred on Nicole Kidman's performance as a sadistic taxidermist.

One of the film-makers' few frustrations with the first film was that the villain and Paddington could not spend much time together until the third act "because if she's got him, she's got him", notes King, "and all of his agency disappears as a character".

With the sequel, however, the hero and villain constantly interact and the film-makers were able to make use of one of Paddington's core qualities.

The little brown bear, who first appeared in 1958 as the central character in author Michael Bond's children's book A Bear Called Paddington, is especially good at pricking people's pomposity, a trait he employs in the new film.

"Paddington is very good at undermining self-important people without being mean," explains King, "and we thought it would be nice to have a character like Phoenix Buchanan, who didn't set out to kill Paddington from page one. That would have just felt very repetitive."

Instead, both Paddington and Buchanan hope to lay their hands on a valuable pop-up book, with the latter hoping that a series of clues contained therein will lead him to a hidden fortune - one which will fund his one-man theatre show.

According to Simon Farnaby, who has a small role in both Paddington films as a security guard and co-wrote the screenplay for the new movie with King, the writing duo simply wanted Grant's character to be funny.

"If we made him an actor, we knew we could have fun with his vanity and his narcissism," Farnaby says. "You can have a lot of fun with a villain in a film like this," he continues. "You wouldn't find Phoenix Buchanan in The Bourne Identity."