Dachs, this is all due to your own time field. My Garmin time was 19:22 and parkrun give me 19:22 as well but I run at a normal speed. Time slows down as you move faster, so on your watch it is 16:28 but to the static observer it is 16:30. All consistent, just google Lorentz-FitzGerald contraction.
parkrun this morning all nice and easy and to plan. From the start I was in 4th and knew two ahead were much faster but did not recognise the other. He dropped off and at 1km I passed him so I was alone in third and simply a case of holding pace to ensure those behind didn't come by. 19:22 is a but slower than maybe I would have hoped for (I have done 19:08 on the course this year and it is worth about 30 seconds over faster courses) but it comes at the end of 2 buys weeks with work in Rome and New York so glad to have topped 40 miles each week as well as the flights and eating. Guy just behind me is in the V60 category so his 19:29 got him over 82%. I'd take that in 10 years time.
Any of the marathon runners on this thread got any advice as to when to decide to pick up the pace if we feel good? I was thinking last 10 miles?
Get to 20 and then take it from there. At 16 you should feel easy, but by 20 it can be totally different. If I was shooting at 3:05 with half an eye on sub-3 I'd try and get to halfway in about 1:31. 90 seconds faster than even at halfway gives you the chance to do the second half 3 minutes slower and hit your target, or stay on pace and get close to 3 dead by pushing the last 6 miles.