The door knocker on the front of Number 10 Downing Street is in the shape of which animals head?

10 Downing Street in London, also known colloquially in the United Kingdom as Number 10, is the official residence and executive office of the First Lord of the Treasury, usually also the prime minister.

Number 10's door is the product of the renovations Charles Townshend ordered in 1766; it was probably not completed until 1772. Executed in the Georgian style by the architect Kenton Couse, it is unassuming and narrow, consisting of a single white stone step leading to a modest brick front.

The small, six-panelled door, originally made of black oak, is surrounded by cream-coloured casing and adorned with a semicircular fanlight window. Painted in white, between the top and middle sets of panels, is the number "10". The zero of the number "10" is painted in a very eccentric style, in a 37° angle anticlockwise. One theory is that this is in fact a capital 'O' as found in the Roman's Trajan alphabet that was used by the Ministry of Works at the time.

A black iron knocker in the shape of a lion's head is between the two middle panels; below the knocker is a brass letter box with the inscription "First Lord of the Treasury".