Easy midweek run with last 15-20 mins faster

This morning around 10:30 a.m. I went out to do my easy run after the short interals yesterday, the plan was to do 8.5k easy with the last 15-20 mins at a faster pace, got to the conservatory in 7:35, then did one lap there and had 13:55, was very slow and easy, was feeling the intervals that I did yesterday, then started to warm up a bit, next lap in 5:57, the next one 5:54, the next one in 5:47, after that the last 2 laps I was going to do a faster pace, I increased the pace a bit, did 5:22 and the last lap in 5:19, from the conservatory to my house which is 1.2k or so, did 6:05, a big downhill there. Honestly I felt a lot better in the faster portion of the run, in the easier portion I was tired from yesterday, but maybe by the time I started to run faster I was all warmed up, who knows!! felt excellent once I warm up,did 6 laps to the conservatory and now I am feeling that the laps go by pretty quickly, total time for 8.5k was 48:35, first half in 25:46 second half in 22:49, huge negative split!!
8.5ktotal, 48:35. Felt great.