All we have is a few unanswered questions and circumstantial evidence.
Albeit none of it definitely proved to be duplicity by Byrne beyond strong circumstantial evidence, but together the coincidences were compelling.
I can't say that for sure, but only because there's no direct proof—only circumstantial evidence.
As early as 1597 the Dutch historian, Wytfliet, describes the Australis Terra as the most southern of all lands, and proceeds to give some circumstantial particulars respecting its geographical relation to New Guinea, venturing the opinion that, were it thoroughly explored, it would be regarded as a fifth part of the world.
This account, which was printed with many circumstantial details by Strype (Eccles.