I knew it was going too well! I planned a slightly longer route as there is more running. This meant the second 5 minute run was slightly up hill. I just shortened my stride, leant slightly forward and aced it. The third run was the downhill and was going really well ... until the final minute ... cramp in the calf! Still, nothing broken ... except my pride!
I'll try again on Friday ... and make sure I drink more water during the day.