Duathlon, why?

Last weekend I had a free morning on the sunday and having been informed of a local Duathlon I decided to give it a go.
I have been threatening myself for sometime to do this type of event and as it was local and an xc event for the mountain bike it seemed ideal.
Whether this was a good idea physically 14 days after the Strathpuffer was unclear, but I had done a bit of treadmill work the previous week and im sure the legs could hold up.
I drove up to Kelling Heath holiday park sunday morning for a 10:30am start, Kelling is a quite location its a holiday park surrounded by cycling and walking trails. And it is surprisingly hilly for Norfolk.
I last time I had ran outside and entered a running event was a steeplechase back in October 2010 so the legs were bound to be a bit rusty.
There wasnt a massive line up and despite being local I didnt know any of the entrants apart from another MTB racer Elliot Lawrence who generally finishes above me in most National events but was less of a runner than me so he was likely to struggle on those legs.
The event was a 5km xc run around fireroad type terrain which consisted of three laps of a loop. This was painful enough but then it was followed a 20km ride over four laps of a different loop this had a killer climb in it which although very short was extremely steep, having heard that in the first of these events only 1 person had made the climb I was on a mission to ride it every lap despite it was likely to be quicker to walk it.
I had lagged behind on the run and only dropped elliot and a veteran runner and Elliot passed to on the last mtb lap as he was clearly much quicker on the downhill sections!
Ride over and then a further 3 laps of the run, but this time gels were a must to keep me go and I was overheating badly having the feeling I wanted to run in just shorts despite the January weather.
I caught Elliot almost instantly on the run and then plodded on to the finish, I had ended up 3rd as another guy ahead had a snapped chain.
The pain which followed was unlike anything I had experienced and the legs were in pain for three days following. But theres another in a week and will I do it again maybe just maybe.
Anyway Thetford Winter series round 3 tommorow so back on the bike for a 4hr stint.