The New Murrey and Blue blog

Now then, I think the Tower of London ought to have a quiet word with Westminster Abbey, because if the boys’ remains have never been found – what’s in That Urn? And by the time they supposedly disappeared, Richard was King, not merely Duke of Gloucester.

“…One of the Tower’s greatest mysteries is the lost princes. These young boys disappeared in the Tower while under the custody of Richard, Duke of Gloucester — it’s widely believed Richard murdered them in his gory path to the crown, but their bodies have never been found…”

https://edition.cnn.com/travel/article/tower-of-london-secrets-england/index.html