He explained: "I wrote it during my holiday. To be more precise, in the hotel's lobby. There was an abandoned piano in the lounge, it was an afternoon after lunch, all the guests were away, the staff were cleaning.
"I sat down in front of the piano and started playing randomly. I had the melody and most of the text after one and a half hours."
McCartney praises his dad James - a keen amateur piano player - for introducing him to music growing up in Liverpool when the family had to make their own entertainment.
He explained to Culture magazine: "My first musical memories come from my dad. He would play the piano at home - he and his friend Freddie Rimmer, both of whom worked at the cotton exchange in Liverpool as salesmen. This was the old days, you know. We made our own entertainment because we didn't have anything else. And those old memories for me are of my dad playing the piano. I would lie on the carpet listening to him and taking it all in."
Paul revealed his father's influence stayed with him as he and John Lennon began writing for the Beatles.
He said: "A lot of what informed the writing I did with John is that early period, and John and I shared that. When we started to talk about that music, John would say 'Oh I love such and such a song.' We didn't like rock'n'roll solely. And I think now if you look at the Beatles body of work it was sort of rock'n'roll informed by this back plot from this complete other era."
Kisses from the Bottom is released on February 7.
