Almost 30 years ago, a book was published entitled The Art of the Deal.

On the cover a large photo of Donald Trump. His surname was in large letters and underneath, as you'd expect, details of the authors: Donald J Trump with Tony Schwartz.

The Art of the Deal was on the New York Times bestseller list for 48 weeks and many commentators say it was instrumental in helping propel Donald Trump from being famous in New York, to being famous across America.

Those commentators include Tony Schwartz - that other name on the front page of the book.

As he tells PM in an exclusive radio interview he regrets ever writing the book and insists that Donald Trump never wrote a word.