It's the investigation that has caused a buzz around the music industry for days: Dispatches sent undercover reporters inside "major fan-to-fan ticket" hubs Seatwave and Viagogo in an attempt to discover who is selling via their websites and "why so many tickets appear at over the face value so soon after the box sells out."

The documentary aired last night on Channel 4 and is now available to watch via the channel's on-demand service, 4oD.

Channel 4 defeated an ...