The Beatles made their US debut on Ed Sullivan's show

They appeared on the Ed Sullivan Show on 9 February, 1964, seen by 73 million viewers and ushering in Beatlemania.

Sir Paul said: "We didn't know what to expect on that first visit - we didn't expect the craziness that was there."

The Beatles were given a President's Award at Sunday's Grammy Awards to mark the anniversary.

It was accepted in Los Angeles by Yoko Ono and Olivia Harrison, the widows of John Lennon and George Harrison, while Sir Paul and Ringo Starr appeared by video link from London.

Starr said: "We had no idea what the Ed Sullivan Show meant, we didn't know how huge it was.

"I don't think we were nervous because we were doing songs that we knew how to play, we'd just done them before and we'd done plenty of TV.

Landing: The band arriving in New York

"But the idea of just coming to America was the mind-blower, no-one can imagine these days what an incredible feat it was to conquer America. No British act had done it before."

The show was seen live by so many people, it was widely reported that it led to the lowest crime rate in 50 years as people stayed at home to watch the show.

The special Grammy award coincides with the release of a DVD of footage shot at the time by documentary makers Albert and David Maysles.

"Thousands of people were showing up to see then," said Albert Maysles.