Well I won't pretend I didn't feel like stopping several times - but I didn't give in to the temptation, and I completed the full 20 minute run.
I even upped my pace for the last minute or so.
Sadly I just crept over the 6 minutes per kilometre mark by 5 seconds, which is really frustrating!
But 3.29 kilometres in 20 minutes is encouraging, I think. Plenty of time to improve on pace.