This was hard work, my legs were not cooperating and I was struggling to keep the pace through out.
I had been aiming for 3:50 on the hard ones and 4:30 on the slower ones. 3:42, 4:27, 4:00, 4:29, 3:57, 4:38, 4:04, 4:48, 3:59, 4:47
Sounds like an excuse but my watch seemed to be measuring the laps at a shorter distance to normal. So may have been closer to the pace than I thought, or I have been slower on the other sessions than I had hoped.