From advanced training methods to a host of young stars and a sound financial footing, the theories have been many and varied.

But according to Arsenal manager Arsene Wenger, the German clubs' success is down to one thing - a winter break.

'The only thing you can say is Germany take advantage of a longer winter break with their club and national teams [more] than anybody else,' Wenger told the club's official site.

'That goes when they are at the big tournaments with the national team and when you play against them in March and April, especially April.

'When you are an English club or a Spanish club, you have a handicap - that is for sure.

'What people forget with a long winter break is during that break the international players get real rest as well, which is not the case in the summer.

'In the summer your players only sometimes get two or three weeks off because they play in the big tournaments, you have to get them back and they do start the new season without being completely rested.

'If you have a big winter break, because the national teams don't play during that break, the international players who are the most exposed to severe physical stress have a real rest as well in winter, and that is a massive advantage.'