Downing Street

[Lorcan]

How many familes reside here? Do only Government members and (I'd guess) security personnel have houses here?

[Octavius]

Downing Street only has four houses along its short length, and is classed as 'exclusive' because its only residents are chosen from the elected Government.

Numbers 10 and 11 Downing Street are the official London residences of the Prime Minister and the Chancellor of the Exchequer - the First and Second Lords of the Treasury. 

Numbers 9 and 12 are the offices of their key staff and colleagues in Government.

Apparently the last private resident of Downing's terrace was a Mr. Chicken (in all seriousness)

[Garriq]

Downing Street is a Treasury enclave. The Parliamentary Secretary to the Treasury has her office at number 12, the Chancellor of the Exchequer (the Second Lord of the Treasury) works at Number 11 and the Prime Minister as First Lord at Number Ten. They are the only two who live in the street (although Tony Blair decided to live at number 11 as the flat is bigger, so Gordon Brown lives is number 10). Recently the Privy Council Office door was given the number nine. That is the Deputy Prime Minister�s office. That building never had a number before.