Here's all you need to know about the front door at No. 10 Downing Street.
Firstly, it was once No. 5 Downing Street but was redesignated as No. 10 in 1779, shortly after extensive renovations that saw three Downing Street properties knocked into one to greatly enhance its grandeur. At the time, the six-panel Georgian door was made of black oak. However, in 1991, whilst John Major was in office, this was replaced with solid black gloss-finish steel, for added security.
There is no lock in which to put a key, and no handle. This is a door than can only be opened from the inside, where – because the brass door bell to its right is for decorative purposes only – a security guard is on duty 24/7, watching security cameras so it can swing open as if by magic on cue to allow in prime ministers, ministers, monarchs and assorted visiting dignitaries.
It wasn't always black. In 1908, Herbert Asquith decreed – apparently at the instigation of his wife – that black was passé. Instead it was given a lick of what historical paint consultants have suggested was either Brunswick Green or Bronze Green. This blip in the door's colour was swiftly reversed by Asquith's successor, David Lloyd George.
If you have ever wondered why those delivering petitions to the Prime Minister can’t just slip their bundle of papers through the shiny brass letter box, there is an easy answer. Despite appearances, it is not a letter-box at all, but a shiny brass plate simply made to look like one (for security purposes) inscribed with the words First Lord of the Treasury. When Sir Robert Walpole took on the house in 1735, that was his official title, though he was de facto Prime Minister. All his successors since 1905 have held both offices simultaneously.
And you may have wondered why the 0 in the No. 10 is slightly tilted. Indeed, it does have a 37 degree tilt, but nobody is quite sure why. It's possible that the official Department of Works, as a result of another round of austerity coincided with the renovation of Numbers 10, 11 and 12 in the early 1960s, had simply run out of ‘0’s. In the spirit of make do and mend, they substituted a spare Trajan ‘O’ as the next best thing.
And you might like to know that if you ever fancy taking a selfie in front of the famous door, you can't, because of all the security measures. However, the good news is that there are suitable alternatives. Nearby, the original oak door is on display in the Churchill War Rooms, or else wander down Whitehall, onto the Strand and turn into Adam Street, where a near identical front door, with similar frame and façade around it, is available free of charge at Number 10. But position yourself carefully for maximum authenticity. This door does have a lock.