Short answers, pulled from the story.
Lancelot de Carle (c. 1508 - July 1568) was a French scholar, poet, and diplomat who served as Bishop of Riez. He worked as secretary to the French ambassador in London in 1536 and later as almoner and royal councillor to the French court.
Carle wrote a 1,318-line poem titled Épistre Contenant le Procès Criminel Faict à l'Encontre de la Royne Anne Boullant d'Angleterre, dated the 2nd of June 1536. It covers Anne Boleyn's early life, her arrest, trial, and execution in May 1536, and may have originated as a diplomatic report to Francis I.
Scholarship now strongly suggests he was. For many years it was believed that a separate Frenchman, Crispin de Milherve, was the eyewitness, but historian John Guy argued in 2009 that French scholars had proven the two names referred to the same man, with the Milherve text shown to have been doctored by 1844.
In June 1537, Henry VIII wrote to his ambassador in Paris calling the poem a malicious tragedy written inside the French ambassador's house in England. He demanded all copies be seized and suppressed, expressing fury that it had been composed on diplomatic premises and then printed in France.
Thirteen copies survive: two printed versions and eleven manuscripts. They are held in the British Library, the Royal Library of Belgium, the Bibliothèque nationale de France, and departmental archives in Bordeaux, Soissons, and Valenciennes. None of the manuscripts precisely matches any other.
Carle served as almoner to Francis I, almoner to the dauphin of France (the future Henry II) from 1545, royal councillor, and adviser to Charles Cardinal of Lorraine and Catherine de Medici. He was appointed Bishop of Riez in 1550 after a diplomatic mission to Rome.