Image copyright Scott Dudelson/Getty Images Image caption Harry Shearer as his Spinal Tap character Derek Smalls

For someone who has made his living from comedy for more than 50 years, Harry Shearer is very serious about politics.

Together with his wife, the Welsh singer-songwriter Judith Owen, Shearer - who does the voices of more than 20 of the characters in The Simpsons, including Mr Burns, Principal Skinner and Ned Flanders - does an annual music and comedy benefit gig for the homeless in the UK and US.

And as a self-described "political animal", homelessness is one of Shearer's major concerns - something he ultimately links to the financial crisis of 2008.

It is not the only impact that crash had, he argues.

"There's a reason why the US, Hungary, the Czech Republic, Italy, Turkey and a few other countries have veered towards a populist strongman kind of leader," Shearer told me.

"It has to do with the fact that when you have a serious economic downturn people lose homes and jobs by the million."

Shearer argues that that only a few people responsible for the financial crash have been held to account for their actions, and that has exacerbated the situation.

"We're basically reliving the lessons of the 1930s," says the 75-year-old, whose Jewish parents left Austria and Poland, respectively, for the US before he was born.

Image copyright Joe Raedle/Getty Images Image caption Shearer prefers to have people impersonate politicians on his comedy shows rather than invite politicians on

The Simpsons has already had politicians, such as the then British Prime Minister Tony Blair, voice their cartoon characters on guest appearances on the show.

So would Shearer like to hear, for example, Donald Trump do the same?

Slipping seamlessly into Trump's voice, he says: "I hate the media. I hate even having to answer that question. I hate to tell you, but you're fake."

Shearer impersonates him on his syndicated public radio programme, Le Show, in a slot called The Appresidentice, where Donald Trump learns to be president.

As himself, Shearer adds: "We don't need politicians to be on a comedy show. We can make fun of them more wittily and wickedly behind their backs.

"We would be serving them because it helps them to humanise themselves. Particularly these days, some dehumanising is necessary.

"Let's have one of the talents do a Donald Trump impression, not make him look like he's got a sense of humour about himself."

Image copyright Monica Schipper/Getty Images Image caption The Simpsons cast and creators celebrated the 30th anniversary of the show in April

Shearer says with a mock sigh that he has been doing the Simpsons for more than 30 years.

"No one expects, unless you work at the BBC, a job to last that long," he jokes, adding that he still has "the same passion and enthusiasm I always had" for it.

The London Christmas show raised money for the West London Mission, which helps the homeless, and the American shows, in Chicago and New Orleans, will raise funds for similar organisations.

"It's an annual event to help with the rampant homelessness crisis that we have in the States as well as here," he says.

Owen adds: "The homelessness in LA is like nothing you have ever seen. Skid Row downtown is a cityscape in itself." She adds that New Orleans, where they have a home, has similar problems.

Shearer and Owen have been following the election campaign in Britain, but it is Prince Andrew's recent interview on the BBC, rather than a politician, that has caught their attention.

Image copyright Mike Pont/Getty Images Image caption Shearer and his wife, Judith Owen, started doing their annual show at home

Shearer's 2011 documentary film The Big Uneasy criticised the "inadequacy" of the New Orleans' levee and water- pumping system which failed to stop the catastrophic flooding of the city after Hurricane Katrina hit in 2005.

Shearer says he now fears for the future of the city after the US Army Corps of Engineers said in April that the $14bn (£10.7bn) replacement system it built will stop providing adequate protection in as little as four years because of rising sea levels and shrinking levees.

"New Orleans serves as a warning because a lot of cities around the world are going to be facing these problems," Shearer says, referring to climate change.

Image copyright Marko Georgiev/Getty Images Image caption Many people were left homeless in New Orleans after Hurricane Katrina hit in 2005

Last month Shearer and his fellow stars of the 1984 "mockumentary" film This Is Spinal Tap reached a settlement with Universal Music Group, which is part of Vivendi, over the film's soundtrack.

The rights to it will eventually be given to Shearer and the other co-creators. Multi-million dollar litigation against Vivendi's film arm, SudioCanal, concerning the creators' profit share, copyright and trademarks in the film is ongoing.

But Shearer doubts the settlement will lead to Spinal Tap reforming.

In 2018, as his bass-playing Spinal Tap character Derek Smalls, he released the album Smalls Change (Meditations Upon Ageing) with its "thoughtful, pretentious and transgressive" songs about getting older.

Smalls performed in a characteristically over the top way at a concert in Los Angeles in November with a full orchestra and a "galaxy of rock stars", including singer Billy Idol, Toto's Steve Lukather and Dweezil Zappa.

Shearer says he could well do some more shows, including in Britain, as Smalls. At nearly 76, he shows no signs of stopping.