IN 2009, CRISTIANO RONALDO moved from Manchester United to Real Madrid in a deal worth £80m ($130m at the time), then a record transfer fee for a footballer. Now he is returning to the English club, over the hill at 36, for a knockdown £12.85m ($17.6m). One question fans will ask is whether Mr Ronaldo can keep his famous number, seven. The number was first given to him by Sir Alex Ferguson, Manchester United’s manager, when Mr Ronaldo joined the club in 2003, and he has worn it every season since bar one, when he moved to Madrid. Edinson Cavani now wears the seven shirt for United, and Premier League rules state that a player must retain his number throughout the season. The club has asked the league to make an exception. How do footballers get their shirt numbers?

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When club football became popular in England in the 19th century, players would appear without a number. Instead they were identified by their position on the pitch. Teams almost always played in a 2-3-5 formation (two fullbacks, three halfbacks and five forwards, plus a goalkeeper), and substitutes were not permitted, so tracking players was easy. The first record of shirt numbers at club level was in August 1928, when Arsenal and Chelsea wore them in matches against Sheffield Wednesday and Swansea Town, respectively. England’s national team didn’t don numbers officially until 1937, when they beat Norway 6-0 in Oslo. In 1939 the Football League Management Committee, the sport’s governing body in England, voted that all clubs must number their players’ shirts from one to 11. From 1965 a substitute was allowed to wear 12, and when a second substitute was permitted from 1987 they usually played in 14 (13 being thought unlucky).

One to 11 corresponded to how the 2-3-5 formation would appear in newspaper reports and matchday programmes. It scanned down the page: the goalkeeper wore number one, right back two, left back three, etc, down to the attacking left winger at 11. These numbers largely endured as tactics changed from a 2-3-5 formation to 4-4-2, which arranged the team in lines of four defenders, four midfielders and two strikers. This meant there was no longer a strict link between positions and shirt numbers (see chart). And not every country’s tactics evolved identically. For example Hungary’s national side in the 1950s numbered their defenders from two to four, with five playing in midfield, rather than in defence as was common in England. In 1953 England lost to Hungary by six goals to three in part because the English players struggled with opposite numbers in unexpected positions. Argentina’s 1978 World Cup squad, meanwhile, was numbered alphabetically (apparently to avoid arguments), so Norberto Alonso, a midfielder, wore the number one usually reserved for goalkeepers.

In 1993 the Premier League scrapped the old system and required each member of a squad to keep his number for an entire season regardless of position, largely to make it easier to identify players. In that season 37 different numbers appeared. Other leagues quickly followed suit. (In international tournaments, such as the World Cup, each player in a squad is assigned a number for the tournament.) Managers tend to dish out the sought-after low numbers to the best players, a legacy of the “first 11” lineup, indicating that they will start regularly. Number nine, usually worn by the centre forward, is often coveted by goalscorers. And some players, such as Mr Ronaldo, make a number their own. Products adorned with his CR7 branding include underwear, shoes, deodorant and a string of hotels. Even if he cannot keep his lucky seven when he restarts at Manchester United, he will always be associated with the number.