Cracked it. Wasn't sure I'd manage this 1st time. Quite heavy legged at the end.
Speed is good though. I have a 5K course and just walk to the end at the warm down pace. 37 mins. Which includes the warm up 5 min walk.
Use of a good chest strap heart rate monitor has been useful. Allowed me to carefully avoid going too fast in the first few weeks. Got to be careful starting in my mid 50s!