“To do a music degree, you have to be able to read music and have a grasp of music theory – I didn’t have any of that at all,” Cullum explains.

Despite being focused on his studies, he couldn’t let go of his musical passion and he continued to play jazz in his spare time, releasing his first album in 1999. The LP Heard it All Before quickly sold out, although Cullum does admit: “There were only five hundred and by ‘album release’ what I really mean is I was selling them out of the back of my car.”

His second album, Pointless Nostalgic, was picked up by an independent label and led to that famous TV appearance.

Now, instead of trying to sell his albums from his car, his life is filled with world tours playing to thousands of people and occasionally checking the charts to see how his singles and albums are doing.

But Cullum struggles to see how much his life has changed.

“I guess it’s changed in that I’ve got a lot busier, but I was always making music anyway. It was all I wanted to do,” he says.

“Obviously, opportunities have come where I’ve been able to get further with my music and I’ve had the chance to work with more and more interesting people. That part of it is strange!”

One thing he can’t deny is that, romantically, his life has had an overhaul in the past few years.

He’s engaged to model-turned-author Sophie Dahl and the pair are set to marry next year. Even though they’re both celebs, don’t expect to see any magazine spreads of the special day.

“We’re going to have the wedding covered by Anglers’ Weekly,” Cullum jokes.

He’s guarded about his fiancee and explains he’s keen to keep his private life just that.

“I think the whole media focus on it is a bit gross. It’s private and personal and it’s just who I am really.

“We prefer to be quiet about us because it’s just to do with us and otherwise it wouldn’t be quite as special.”

So there won’t be a reality TV programme where the two are followed around with TV cameras then?

“No! That’s definitely not for us, plus I think people would be bored by us.

“There’s not that much to see really.”

Although he’s keen to keep his relationship away from the spotlight, he’s more than happy to entertain his fans.

“To have an audience is a privilege and obviously going out and playing is what I love to do,” says Cullum.

“So, even though touring can get tiring, it certainly never gets old. It’s still just as exciting.

“I think the time it stops getting exciting I probably shouldn’t be doing it.”

He continues: “I’m proud of just being able to continue to release records and tour and be able to sustain a career.

“I didn’t realise until now how much easier it was to be a new artist, having that new car smell was a great selling point and trying to recapture that with my audience is impossible, so I have to focus on putting out great music.

“I don’t really feel like a veteran in the business but five records in I guess I am!”

Cullum is particularly happy with his latest album: “When I look back to my start in music, I think about how much I’ve grown in the music industry.

“When I listen to the new album in context to what I’ve done before, I see a real arc upwards in terms of my musical achievement.

“That makes me really happy. It’s great to think I’m improving with every record.”

Looking back on the last decade, Cullum recognises that he’s very lucky both in love and career.

So does he acknowledge the impact Parkinson had on his life? “I was very lucky to have that opportunity. There are a few things which led to my success but that was definitely an important one.”

JAMIE CULLUM is playing Liverpool Philharmonic Hall on May 14, 2010.