"If I'm on a train, I see everybody else just looking at their screens," McCartney tells BBC News. "But I'm looking out: 'Oh look, there's the London Eye! There's the River Thames!'"

McCartney continues, "Sometimes they do look up and they take a little picture and they sell it to the newspaper. And this is the price of fame."

The songwriter recently put this to the test in the lead up to his concert in New York's Grand Central Station by wandering through the atrium and filming the audience on his iPhone — "just to get a feel of it," he explains to the BBC. He wasn't noticed once.

It is just one element of the fame survival skills McCartney has nurtured since the early days of the Beatles, when the band were literally chased down the streets by screaming fans. Instead of panicking or beefing up their security, John, Paul, George and Ringo learned that the best way to deal with Beatlemania was to simply keep moving and keep calm.