Guardian. (Who got it from the Times, but that's a subscription link and all.) Apparently it's a teaser snippet from Charles Norton's new book Now On The Big Screen: The Unofficial And Unauthorised Guide To Doctor Who At The Cinema, a guide to the troubled times when the BBC was attempting to turn their Children's Own Programme into a major motion picture. Norton's book is available in soft or hardcover from Telos, if you'd like a copy.
It was apparently mooted some time in 1988, so after the oddity of the George Lucas Disney production Captain Eo, not to mention the star's own Moonwalker, which actually do almost make sense of the casting. (Quite late that year, presumably, since Moonwalker came out in October that year.) Den of Geek did a bit more digging and says that Bill Cosby was second choice. Only seeing as he was right in the middle of The Cosby Show just then, somehow he'd seem even more improbable than Jackson. And of course old-skool fans will be already familiar with a lot of improbable Hollywood names going around for the Doctor in the 80s and 90s (Donald Sutherland, Dudley Moore). Jean-Marc Lofficier's book The Nth Doctor listed some of these, but it focuses more on the 90s material, so hopefully Norton will provide a lot of fresh new info for us to enjoy (seeing as Norton's book does have a picture of Peter Cushing on the cover, and Tom Baker in the outfit he was wearing when they were talking about the Scratchman project, it must be fairly comprehensive).