Sir Winston Churchill would think Donald Trump is an idiot, according to the man playing the former Prime Minister in a new film.

Brian Cox will play the lead role in the Churchill, which depicts the build-up to the 1944 D-Day landings.

The Scottish actor says his latest character would not have been a fan of the American president, or current UK foreign secretary Boris Johnson.

The 71-year-old Dundee born actor said: "Churchill would have thought Donald Trump was an idiot.

"He was a man of principle and I don't think he would have liked Boris Johnson, who wrote a book about him.

"Johnson thinks of himself as Churchill but he hasn't got the gumption of Churchill. He is an opportunist, and he is about as deep as a blackhead."

Cox had to gain weight and shave his head for the film, which also stars Miranda Richardson as Clementine Churchill and John Slattery as Dwight D Eisenhower.

He revealed he used electric cigars instead of the real thing while he was in character as the wartime leader.

Cox said: "Different lengths of electric cigars, designed for us - brilliantly,".

The Braveheart and X-Men actor also spoke of what he said was an "insidious" caste system in British society and said he and Welsh actor Sir Anthony Hopkins both sensed a certain snobbery.

He said: "Tony Hopkins and I have one thing in common: we are not English. It's a very interesting thing about the feudalism of English society.

"It's about who you are and where you come from, how you operate within that world. It's the caste system, which still exists and is actually even worse now. I mean it really is - it's more insidious."

Cox, who plays Colonel William Striker in the X-Men movie franchise, campaigned for Scottish Labour in the 2007 Scottish Parliament elections but endorsed the SNP in 2011 as a result of their higher education policy.

He then went to campaign for Scottish independence in 2014 before officially quitting Labour and switching allegiance to the SNP in 2015.

Churchill opens in cinemas across the UK on Friday, just over 73 years on from the Normandy landings on June 6, 1944, known as D-Day.