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The POD is in 1527 to 1528 that Henry VIII Henry VIII decides that Catherine of Aragon has to die, so he can marry Anne Boleyn. This TL's version of Henry VIII does not have as much of a conscience than he did in OTL.
Therefore Catherine of Aragon is murdered in her bed on the orders of Henry VIII. However the official explanation for Catherine's death is that she died of “pure displeasure and melancholy" or something along that line. Only a few people (sworn to absolute secrecy) apart from Henry VIII know that Catherine was murdered on his orders.