Mary felt quite shocked when seeing this figure in the photo and when she showed it to the rest of her family, they all agreed that they boy had a strange pallor to his skin and looked distinctly different to Kayleigh and Andres (whose hand you can see). The area where the photo was taken was very small and no one would've been able to pass as it was a narrow area. Due to the long and bloody history of the Tower, Mary felt that this ghostly figure may have been one of the Princes, who were said to have been locked up in the tower by their Uncle, Richard III and then were murdered there. No one is quite sure what happened to these Princes, who disappeared when they were only 12 and 9. They were referred to as Princes but really the 12 year old was Edward V, King of England and Richard 9. of Shrewsbury, Duke of York.
Whoever that small ghostly figure was, it certainly is an intriguing photo and to my eye, the boy looks as though he's wearing some sort of ruff or heavy collar. What do you think?
For some historical facts about the Tower of London, go here and for the Princes in the tower, go here