She dished she was in a 'bleak mood' when she jetted into Los Angeles from London on Wednesday.

But JK Rowling refused to talk about Donald Trump's election as she promoted Fantastic Beasts And Where To Find Them, at a press conference with star Eddie Redmayne ahead of the New York premiere on Thursday.

The author, a vocal critic of the president-elect, said she wanted to 'focus on some good things.'

On the promo trail: JK Rowling Donald TGrump critic refused to talk about his election as she promoted Fantastic Beasts And Where To Find Them, at a press conference with star Eddie Redmayne ahead of the New York premiere on Thursday

The 51-year-old revealed she came up with the Harry Potter prequel story 'a few years ago...partly informed by what I see as a rise of populism around the world.

'If you have read the Potter books, you'll know this period of history threatened to become very dystopian. You were looking at the rise of a very dark force.'

Rowling added: 'Last night I was in a kind of a bleak mood boarding the plane and I thought "I need to work."

'I got out the second screen play and worked on that and it made me feel a whole lot better. '

In trouble: Eddie stars as Newt Scamander a wizard who inadvertently unleashes a plague of magical beasts on New York 70 years before Harry Potter reads his book at Hogwarts

Fantastic Beasts is the first of five films and it has been reported that a sequel may include a gay relationship between the character Grindelwald, played by Johnny Depp, and a young Professor Dumbledore from the original Harry Potter stories.

Addressing the rumours, Rowling said: 'I can't tell you everything I'd like to say because obviously it's a five-part story and there's lots to unpack in that relationship.

'As far as his sexuality is concerned, watch this space.'

Art imitating life: The 51-year-old revealed she came up with the Harry Potter prequel story 'a few years ago...partly informed by what I see as a rise of populism around the world'

Eddie, who plays the lead role of Newt Scamander, said he was in 'shock' when Rowling announced there would be five films in the series.

'So much about this process has been top secret that it was secret to us,' the 34-year-old said.

'Our scripts were put in safes at the end of the day, but all for a reason we understand, which is there's such an appetite for the world and the universe and the stories that Jo creates.

Keeping quiet: She wouldn't confirm rumours about a possible gay relationship between Johnny Depp's character Grindelwald and a young Dumbledore saying:, 'Watch this space'

'In this world of so few surprises, it's wonderful to try and keep those secrets.'

Newt is a wizard who inadvertently unleashes a plague of magical beasts on the city of New York - 70 years before Harry Potter reads his book at Hogwarts.

The world premiere of Fantastic Beasts And Where To Find Them takes place at Alice Tully Hall at the Lincoln Centre in New York City on Thursday evening.

The film goes on wide release in the US and UK on November 18.