Much earlier in the year I was trying to increase my stroke rate to gain some speed. My arm turnover is slow and may well be associated with a drawn-out glide phase. So today I tried sets at 64, 65 and 66SPM hoping to get some good times, I remembered 66SPM being a good rate for me. I got a good workout but unfortunately the pace didn't improve. Even my first set at 65SPM was at a below normal pace. This suggest quite strongly that the stroke rate was too high for me to be effective.
Some final sets with bilateral breathing and a standard pullbuoy with a greater tempo were disappointing too.
Looking back to April 2018 it seems that 62SPM is closer to my ideal turnover than 66SPM, I'd remembered incorrectly, even from earlier in the month...
It's also possible that I'm tired, yesterday's run was the slowest I've ever done for that regular route.