Finally i’ve found the typeface of London’s street signs. It’s called Transport and was created by Margaret Calvert and Jock Kinneir in 1963. I love this font, though you see it quite often here.

Some might recognize a slight resemblance to two of my really favourite typefaces, DIN 1451 (German Standard Committee, 1936), which is used for the German transport system and the improved version FF DIN (Albert-Jan Pool, 1995). The roundish letters of „Transport“ like C,O,Q are much rounder tough than those of „DIN“, but in a nice way.