In that year Thomas Nashe implies the existence of such a play in his introduction to Robert Greene's Menaphon:
Because Nashe apparently makes allusions to Thomas Kyd in the same passage, and because of similarities between the Shakespearean Hamlet and Kyd's Spanish Tragedy, it is generally accepted that Kyd was the author. More controversial is the question of how much of Thomas Kyd's play survives in William Shakespeare's version, especially the first quarto of 1603.
Some anti-Stratfordians claim that there was no Ur-Hamlet, and that the references are merely signs that the Shakespearean Hamlet was written earlier than the generally accepted date. Only a few orthodox Shakespeareans, like Harold Bloom and Peter Alexander, have believed that Shakespeare himself was the author.