What does Boris know?

It's to protect the City of London financial district from anti-capitalist demonstrations. There's already a ring of steel around the area and it's become a virtual police state. (The City of London Police are entirely independent of the Metropolitan Police). Anyone seen loitering in the area or filming without permission is very quickly escorted out.

But they still need the (as yet ungiven) permission of the home secretary to be used don't they?

http://www.channel4.com/news/may-still- ... s-purchase?

Speaking during questions at London's City Hall, Boris Johnson said his decision to buy the vehicles was not designed to put pressure on the Home Secretary, and described the idea that Mrs May might decline to approve their use as "highly unlikely".

The London mayor dismissed suggestions that the decision to buy them was part of a proxy war between him and Mrs May as "absolutely nonsensical", adding "this is something I know is supported by the Prime Minister, it is something I know is supported by people across politics, and we're going to get on and do it."