Red and yellow cards were the brainchild of Ken Aston, a former teacher and soldier in the British Army who, after a spell as a referee, became chairman of FIFA's international referee's committee.
Aston had been the referee at one of the most violent games ever played, the infamous Battle of Santiago, between Italy and Chile in the 1962 World Cup. He is seen below, on the right, escorting Italy's Giorgio Ferrini off the pitch.
But the idea came to him four years later, in the aftermath of England's bad-tempered quarter final match against Argentina in the 1966 World Cup in England. During the course of the match, Argentina's captain, Antonio Rattin, had been sent off in controversial circumstances by German referee Rudolph Kreitlein for "violence of the tongue". Rattin had refused to leave the pitch amid chaotic scenes at Wembley Stadium.
England's players had also been verbally cautioned by the German referee during the game, but, because of the language barrier, some of them were unclear whether their bookings were official. The day after the match, a member of England's team called Aston to clarify whether Bobby and Jack Charlton, in particular, had been cautioned after it was reported in the newspapers that they had been and faced suspension from future games as a result.
It was then that Aston's idea for a visual, universal system that overcame linguistic differences was born. Recollecting the moment on FIFA's official website, Aston remembered driving through the streets of London. "As I drove down Kensington High Street, the traffic light turned red. I thought: 'Yellow, take it easy; red, stop, you're off."
The system was first used at the 1970 World Cup and was quickly adapted at all levels of the game.