If a nuclear missile were to hit central London, how far out would the damage reach?
It all depends on your definition of “damage” is. If it’s a single broken window in a house then it’ll be much larger area than the following most common damage zones: fireball, radiation, 20 psi air blast, 5 psi air blast, and thermal radiation.
Since most Americans have gotten over that little War of 1812 when you torched our White House, I’m going to assume it’s a Russian RT-2PM Topol, or as NATO calls it the SS-25, with a 800 kiloton warhead with an airburst about 1 mile overhead.
I’m also going to use the NUKEMAP website because it’s quick and easy to use.