Six laps of a 37.73 mile circuit at speeds approaching 200mph? A 5000 mile marathon over rock, sand and every other surface imaginable? 24 hours of flat out neck and neck racing on a GP circuit? A one day battle against 1500 other offroaders and the fearsome Iron Giant?
There's many contenders for the title of 'toughest biking event' from the Isle of Man to the Dakar, from the Le Mans 24 hour race to the Erzburg Rodeo, each one testing rider and machine to their limits.
But which do you rank as the toughest of the tough, the hardest of them all?