This week Ruth Alexander looks at Manchester United versus Real Madrid in the last 16 of the Champions League. Real Manager Jose Mourinho says this was the match the "world has been waiting to see". It pitched two of Europe's biggest clubs against each other in what is a supposed to be a money spinner for broadcasters and sponsors alike. But how do we know how big the interest is? Manchester United claim 650 million fans worldwide, but how can we know? Nick Harris of SportingIntelligence.com and Richard Brinkman of KantarMedia help us look at the figures. Also: this round of the Champions League has been a statistical surprise. The rehearsal and the real draw threw up the same fixtures meaning that the same teams were picked to play each other in both draws. Statistician Michael Wallace helps us calculate the chances of this happening.