OK, that was good - with treadmill always best to be short and sweet. I was having a hard time keeping the work intervals in zone 3 rather than bumping up into zone 4; it's a while since I've done a HR-based treadmill workout, I forgot how it works with the lag time...
5 x 3min Z3(4), 1min recovery
I am keen to increase run frequency, and I think the best way to do that is to include several 30-minute runs in the week rather than trying to have lots of longer ones. We will see how it goes - back to NYC tomorrow evening, Thursday will be a bit of a wash but hoping to be fully on board with normal fitness schedule for Friday and Saturday.