In reply to The New NickB:
My experience is exactly as NickB the New - 3:50 -ish during a race, but in training, my garmin often "shocks" me by saying I'm "only" running at 4:45 pace, even tho I feel like I'm going faster. No biggie.
Keep it varied, & keep having rest periods as well as consistent training. Also, don't worry that you're only as good as your last run. It's all £££ in the bank.... good luck!