Sir Paul McCartney has swapped stadiums for the back of a London shop as he entertained one of his smallest audiences for years – to a crowd of little more than 30 people.

The star was aiming to give inspiration to musicians and aspiring songwriters after they assembled to hear him give a 42-minute talk about composing, as well as taking questions about his experiences.

The superstar was appearing at the invitation of model Lily Cole, and decided to return a favour after she appeared in the video for his single Queenie Eye.

Sir Paul McCartney
(Ian West/PA)

He agreed to speak at the small gathering run by Lily’s community website Impossible which encourages people to share their time and skills with others.

Guests gathered at an anonymous shopfront in Berwick Street, Soho, before taking their places inside to hear the former Beatles star discuss his art – just a stone’s throw from where he had performed an intimate show at the 100 Club, a little under four years earlier.

Sir Paul was outlining how he had written the song Hope For The Future which was commissioned to appear in the video game Destiny, and which will be released as a single in its own right on December 1.

Lily Cole Sir Paul McCartney
(Ian West/PA)

But he also told the fans – who had landed their places at the talk after a call-out online by Impossible and his own website – about writing with his old bandmate John Lennon and the importance of practising “a lot”.

The star also spoke about how he had based his song Blackbird, which was released in 1968 on the White Album, from a short passage in Bach’s Bourree in E Minor which he had previously played as a “party piece”.

“I just followed the trail of these two notes going together – a bass note with a melody. It was basically variations on that little trick of Bach’s,” he said.

Sir Paul McCartney
(Ian West/PA)

Sir Paul also had advice for an aspiring 13-year-old who had written a set of 12 songs over the summer which she wished to release as an album.

“Have you recorded them? Well that’s the first thing,” he told her. “Just record them all so you have got them as a little body of work – and then just keep going.”

Lily Cole Sir Paul McCartney
(Ian West/PA)

One fan had travelled from Belgium this morning after landing a place at the event.

“You came from Belgium? That’s really cool – respect!” Lily told him.

Just a week earlier Sir Paul was headlining shows in Brazil and he is due to return to the country for further dates at the weekend.