More from our Political Correspondent Simon Harris:
Johnson: The 20/20 vision is there as another bench-marking tool but it's not the only one. @itvlondon
Johnson and Hogan-Howe are asked why rape is not included in the list of seven targeted crimes. @itvlondon
More top news
The 34-year-old victim was left with a huge gash across her nose and face. Police need to find a man seen on CCTV.
The girl was travelling on a train from London Liverpool Street to Romford in Essex after going to see the poppies at the Tower Of London.
Wealthy businessman Ivan Massow wants to succeed Boris Johnson at City Hall in 2016.