Today was a basic 15 km, fairly slow and gentle and very slow after Monday! However Tuesday's swim seemed to go fairly well and I seemed to be in a good equilibrium between breathing and swimming which promises progress. Yesterday's circuit had left me with tired legs so a fair time was a good outcome. Although there is a strong argument that some speed is essential it is also well reported that base training is the foundation; this article makes that sound complex though! I'm sorry to say that I don't have much plan to my distance, except that any medium length trail run in Sheffield will have a variety of physiological demands due to the hills!
By the way, another Strava Course Record of mine lost, it looks as though there is a new entrant in the area who is quite fast (5km in 18 minutes) ad taking similar routes to me.