Champions League - English Dominance

This season there are four teams from the same country in the Champions League quarter-finals for the first time ever.

While Italy, Germany, Spain and Turkey have to make do with one side each, the Premier League's big four have all made it through.

The progress of Liverpool, Arsenal, Manchester United and Chelsea has shown the strength of the Premier League - and with two of them drawn together, England is guaranteed at least one semi-finalist.

Never before has one country dominated to such an extent, so why and how has it happened? And will it continue?

If so, what does it mean for other leagues around Europe, as the best players head for the Premier League in large numbers every summer?

And could the future of the Champions League be under threat if this trend continues?