Sir Paul McCartney has paid an emotional tribute to legendary producer Sir George Martin.

The 73-year-old musician worked closely with Martin during his time in The Beatles, with the musical director even earning the nickname the 'Fifth Beatle' due to his work with the band.

Following the tragic news that Martin died at home on Tuesday (08Mar16) aged 90, McCartney penned a lengthy tribute to him on his official website.

"I’m so sad to hear the news of the passing of dear George Martin. I have so many wonderful memories of this great man that will be with me forever," he wrote. "He was a true gentleman and like a second father to me. He guided the career of The Beatles with such skill and good humour that he became a true friend to me and my family. If anyone earned the title of the fifth Beatle it was George. From the day that he gave The Beatles our first recording contract, to the last time I saw him, he was the most generous, intelligent and musical person I’ve ever had the pleasure to know."

Recalling one of his favourite memories of Martin, McCartney said he was unsure about the producer's suggestion to include a string quartet on iconic Beatles track Yesterday. But after making it into the recording studio and hearing the finished product, McCartney knew he was in the wrong.