Brexit: The Musical hits London theatres this week, with its writer David Shirreff calling it "a bit like a Gilbert and Sullivan opera".

Based on the UK's withdrawal from the European Union earlier this year, Brexiteer and UK foreign secretary Boris Johnson is given a starring role in the play.

"Boris Johnson is a gift to put on stage because he's such a character anyway. You expect silliness to come out of his mouth and he doesn't disappoint," former journalist for The Economist Shirreff said.

"I loved his little aside to John Kerry [US Secretary of State] when he was being booed at - "it's going well John, I feel at home"," Sheriff said, referring to an awkward press conference Johnson hosted with Kerry in July.

"The trick (to play Boris Johnson) is mainly to pretend to know what you are doing but really sound like you don't have a clue of what's going on at anytime," actor James Sanderson told AFP.

Acting UK Independence Party (UKIP) leader Nigel Farage is played by Jack Bradley, and sees his character sing songs about the glories of the people and Britannia. Prime Minister Theresa May, played by RJ Seeley and portrayed as a Big Brother figure, sees May keeping a strong hand on the Brexit tiller.

"The situation is that Brexit is a complete mess", Shirreff said. "The world doesn't need Brexit, that's my view, so I was just trying to make it look as ridiculous as possible on stage."

Sheriff is hoping to incorporate Farage's recent run-in with President-elect Donald Trump into later showings.