Fleet half

This half marathon was only just down the road for me and was pretty flat - what could be better?
So after a short drive and a short walk I'm there, far to early and feeling like billy no mates standing around on my own. The park soon filled up and then we're ready to go.

The first couple of miles included a hill (twice!) and my left thigh was really paining me. I don't know why and it was only really 'can I do this' bad on downhill bits (not many of those though thankfully).

Plodding along at a comfortable pace, missing mileage markers, until the 4m post when I realised I was still doing the same as at Reading, 10min miles.
Tried slowing down and some walking but that was pretty uncomfortable so I just carried on crossing the line in a clock time of 2:11.

Good bits
Great crowd support (including my daughter and neighbour), good country roads/views, flatish course, know what my comfortable/natural pace is, ran with batman and robin for a few miles, beat the bloke carrying 2 oars.

Bad bits
Not fit enough to do my prefered pace for much more than 13m, none the wiser as to a plan for marathon, really painful right thigh muscle for whole race, no goody bag.

I'm sure there's other stuff but I'm tired, come to think about it I'm physically tired all day everyday now.

Is it just me?