The London Mayor Boris Johnson has said stories that he is planning to be Prime Minister should be "knocked on the head".
During an argument with the London Assembly Chair Jennette Arnold, he laughed off a suggestion that he was "being prime ministerial".
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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.