The two mayors briefly took in the view from the balcony of City Hall before returning inside to exchange novelty gifts.

Mayor Bloomberg was first to present Mr Johnson with a Tiffany box containing a crystal Big Apple paperweight, before the flamboyant Tory returned the favour with his garish item of clothing.

Handing over the plastic wrapped shirt, he quipped: "This is not the most handsomely wrapped present."

The pair then retired behind closed doors for talks, where they are expected to touch upon policies relating to transport, education and skills, congestion and the environment and policing.