A collection of previously unseen Beatles memorabilia from Sir Paul McCartney’s personal collection have revealed the impact of the musician’s family on his songwriting.

Handwritten lyrics, postcards and photographs collected by Sir Paul are to be unveiled to the public for the first time at the British Library’s new exhibition, Paul McCartney: The Lyrics.

In addition to around 35 documents from his personal archive, the exhibition also features quotes from Sir Paul which offer an insight into his creative process.

Handwritten lyrics for Yesterday (British Library/PA)

In one, displayed alongside a photograph of his father Jim, Sir Paul says that although there are “so many” people who influenced his songwriting, his parents had a huge influence on the way he approached his music.

“Thinking about songs that I’ve written at every stage of my career, I came to realise that my parents, Jim and Mary McCartney, were the original inspiration for so much that I’ve written,” he said.

“My mum was very reassuring and, like so many women often are, she was also the one who kept our family going. She kept out spirits up.”

He added that his father “was loaded with colourful expressions, as so many Liverpool people still are today”.

“He loved to play with words, juggle them in his head, and he had loads of little sayings that were sometimes nonsensical, sometimes functional, but always rather lyrical.

“When he was shaking your hand he would say, ‘Put it there if it weighs a ton’.”

Linoleum at Paul McCartney’s former home
Sir Paul McCartney (Ian West/PA)

Also in the exhibition are an original drawing by Sir Paul, 79, for the single Put It There and a postcard of the Beatles in Hamburg.

There is also a collection of photographs taken by Sir Paul’s family, including one of him playing guitar with John Lennon at home in Liverpool.

Andy Linehan, curator of popular music recordings at the British Library, said it was “quite exceptional” for Sir Paul to have kept so much archive material “in such an ordered manner”.

Speaking to the PA news agency, curator of contemporary literary archives Greg Buzwell added: “Paul wrote from inspiration. He’d just see something and say, ‘I will write something about that’.”

Sir Paul had a “freestyle” approach to songwriting, he said, adding: “I think he took inspiration from just about everything.”

The free exhibition opens to the public on Friday and will remain at the British Library in London until March 13.

The exhibition opens in the week Sir Paul releases his new book The Lyrics, which also features unseen Beatles material from the musician’s personal collection.