If Joe Bloggs ran the autocue screen and got an advance copy of the speech, would it be illegal? What if he overheard Buffet practicing his speech and bought i

If Joe Bloggs ran the autocue screen and got an advance copy of the speech, would it be illegal? What if he overheard Buffet practicing his speech and bought it - would that be illegal? If he were to tweet "I Joe Bloggs heard Buffett saying he is about to say something good about Microsoft" and then buy a few seconds later, would that be public information? When does public information change from being private information to being public information nobody has noticed?