So this sandwich is "The best sandwich I've ever had" A quote from somebody called John Thorpe.
Maybe giving this some personal reference gives it some convincing credibility. Just because it's been said does not make it true. Even if we assume John is sure and true, the credibility of the quote depends rather more on how many sandwiches our dear friend John has had.
Of course if this was the first sandwich that John ever had - it would still be the best - but it would also be the worst of course...