@Whorty, you are not wrong, I definitely hit the wall and coasted in completely spent.
I was aware that there was 4 miles of climbing, nothing too serious, but enough that I knew I would need a couple of minutes lead at the bottom of the descent, to stand any chance of staying away. So I probably put too much into the downhill and paid for it later. I think I had about 45 seconds lead when it levelled and I was picked off one at a time, and I had nothing left when you caught me.
I might give it another go, and try my coasting tactic on the downhill, and see if I can fair a bit better on the second half of the course.