Meeting Gandalf would be quite out of this world, but encountering Gandalf side-by-side with Star Trek’s Jean-Luc Picard took me to a whole new space-time continuum.

This most unlikely of interviewing assignments also turned out to be one of the most entertaining. Wise old wizard Sir Ian McKellen and Starfleet commander Sir Patrick Stewart turned up in Soho this morning to publicise their latest X-Men movie.

They reprise their roles as Magneto and Professor X respectively, forced in old age to confront the errors of their youth. Both actors appear to find the focus on ageing particularly poignant.

Sir Ian was diagnosed with prostate cancer a few years back, and as Sir Patrick starts telling me: “I do find that I have a much more urgent feeling to enjoy myself now”, his co-star interjects: “I thought you were going to say an urgent need to go to the lavatory.”

If the film deals with the wisdom of age, it’s as much about mankind’s persecution of minorities – the mutants, as Sir Ian freely recognises.

“When Bryan Singer [the X-Men director] asked me to be in these films he sold it to me on just this point: as a gay man you can identify with mutants – people who have talents [but] are despised by society as they’re different…

“In many areas of the world being gay is still a mutancy which is clearly not tolerated in some societies. You can be put to death for your sexuality. Not in this country. We have advanced – it’s been one of the great joys of my life – since these films have been made.”

So what does he make of the Ukip leader Nigel Farage’s declaration over the weekend that most British people over 70 are “uncomfortable” with homosexuality?

“He hasn’t talked to this over-70-year-old or this one,” he says, gesturing at Sir Patrick. “Farage needs to get out more…Gay people come and get married. The story is over.

“People shout louder and louder because they are so frustrated their opinions and their prejudices have not been confirmed by the rest of society,” he adds.

To Sir Patrick, a long-standing Labour party member, victory for a bearded drag queen in the Eurovision song contest is an indication of just how far out of step Farage is.

“I think it was one of the brightest moments in the Eurovision song contest for years and years,” he says, although Sir Ian isn’t sure Conchita would have got his vote. “It’s not a look I particularly like,” he remarks.

It’s rare for this most harmonious of couples to disagree on anything. Sir Ian officiated at Sir Patrick’s marriage last year, and their “bro-mance” has tickled Hollywood pink.

They’ve posed on Santa’s lap, impersonated each other, and taken to the stage together. In some ways it’s an unlikely relationship. Sir Ian is a Lancastrian who went to Cambridge University, Sir Patrick a Yorkshireman who left school at 15.

But their friendship is patently heartfelt and unusually tactile. During the interview they were forever smiling at each other, patting each other endearingly – even finishing each other’s sentences.

I asked them to sum up their relationship with a Twitter hashtag. “#AREN’T WE LUCKY” scribbles Sir Patrick. “#eternal” scrawls Sir Ian.

As they hold the tributes up for the camera, I can’t help but notice they’ve equalled each other in the sincerity of their compliment – the only difference being the Yorkshireman displays his piece of paper portrait-style, while the Lancastrian goes for landscape.

“I’m upright, he’s horizontal,” quips Sir Patrick, and we all dissolve into laughter. It surely beats working for a living.

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