The UEFA Champions League comprises three qualifying rounds, a play-off round, a group stage and four knockout rounds.
In matches in the three qualifying rounds and the play-off stage, clubs play two matches against each other on a home-and-away basis. The club which scores the greater aggregate of goals qualifies for the next round, with away goals and then penalties used to determine the winner in the event of a draw.
The ten winners in the play-off round ties – five from the best-placed path and five from the champions path – join 22 automatic entrants in the 32-team group stage. The clubs are split into eight groups of four teams, who play home and away against each of their pool opponents between September and December to decide which two teams from each section advance to the first knockout round. The third-place finishers in each group enter the UEFA Europa League round of 32.
From the last 16 until the semi-finals, clubs play two matches against each other on a home-and-away basis with the same rules as the qualifying and play-off rounds applied. In the last 16, group winners play runners-up other than teams from their own pool or nation, while from the quarter-finals on the draw is free.
The final is decided by a single match, which this season will be played at Wembley Stadium, London on Saturday 28 May.
Further details, including the criteria for separating teams that finish level on points in a group, can be found in the official competition regulations.
Documented evidence of ball games being played in London dates back to the 12th century, with the first mention of 'footballs' coming later in 1314 when the lord mayor of London, Nicholas de Farndone, issued a decree outlawing their use on behalf of King Edward II.
The game has come a long way since, of course, and the version we know today first emerged when a set of rules was drawn up by the newly established Football Association at London's Freemason's Tavern on 26 October 1863.
The end of the 19th century was boom time for the sport as clubs sides sprang up across the capital, with the oldest still in existence generally accepted to be Fulham FC, formed in 1879. The final of the world's oldest football competition, the FA Cup, has usually been held in London too, kicking off with the 1872 showpiece won by London outfit Wanderers FC at the Kennington Oval. Wembley then took over the hosting of the event from 1923 to 2000, before the rebuilt venue resumed that duty in 2007.
Long known as the 'Home of Football', Wembley has served as a focal point for the game in London, staging the climax of the football tournament at the 1948 Olympics and the 1966 FIFA World Cup final, not to mention five European Champion Clubs' Cup and two UEFA Cup Winners' Cup showpieces. The English capital nonetheless remains a vibrant hotbed of club football, with no fewer than five Premier League teams in 2010/11 and 13 altogether in the top four divisions.
The city's sides cannot match the trophy hauls of north-west giants Manchester United FC and Liverpool FC – particularly in Europe, where London still awaits its first continental champions – but the likes of Arsenal FC, Chelsea FC, Tottenham Hotspur FC and West Ham United FC can look back upon many glorious achievements down the years. Fittingly, the first three of those clubs started off down the road to Wembley this season as London provided three UEFA Champions League group stage contenders for the first time.
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