In searching for Cecily Nevill’s letter to Margaret of Anjou, I also found this. I’m assuming that the confusion about its intended recipient is well and truly cleared up. Rawcliffe* thought it was a letter to Edward, earl of March, though it would have been extraordinary if it was. But as she also is prepared to believe that Edward threatened to march on London at the head of an army at the age of ten, her confusion is perhaps not quite so surprising. Bearing in mind that around this time Edward and his brother Edmund sent their father a letter asking for help against the bullying Crofts, I think that if he’d had an army powerful enough to threaten London he’d have been able to sort this out himself! Pugh** (correctly) links it with Henry Holland, duke of Exeter, who was, at the time it was written, fomenting rebellion (or trying to) in the north of England alongside those two well known rapscallions, Thomas and Richard Percy. (below is the version as found in Rawcliffe.)
The letter is dated 8 May 1454.