I have just read Alison Weir's ' Elizabeth of York' - and half way through I suddenly thought - Margaret Beaufort murdered the princes in the Tower - of all people she wanted them dead because her son Henry had a very shaky claim and a marriage to Elizabeth would help his claim, but not if the princes were alive and Margaret had plotted to make Henry the king for years and she was married to Stanley who supported Henry at the last minute at Bosworth. I didn't realise until I read this blog that Margaret had been considered as the culprit previously but it was more or less rejected because no-one knows where she was in the summer of 1483 - but she was in touch with Elizabeth Woodville via her priest who visited Woordville in sanctuary - so she could easlly have organised the deaths of the princes if she wanted to.
I agree! I think that she convinced Stanley to speak with Richard, to convince him,that the Boys were a major threat to his claim and so then he ordered their murder! Margaret wasn't directly involved but she was a very smart woman who wanted her son on the throne!
Stanley then of course backed Henry Tudor and Margaret got what she wanted! Her son as king, with no princes to take that away from him!