Well that started well. Walk the mile to the leisure centre, changed and went to the gym, a 5 minute warm up walk and set off with my normal trot pace. 2 minutes later, a twinge in my left hamstring, slowed to a walk again and the twinge went away. Tried upping the pace and it came back.
Discretion being the better part of valour, decided to leave the celebratory run until another day. I did however take the long (2 and a half miles) route back home.