Railperf, I have done two London-Edinburgh returns since the December 2025 time table came in, and have been impressed with the service when it’s working well. Both my London-Edinburgh runs have performed better than Edinburgh-London, with London-York timed in 103.41.9 mins and the other London-York run in similar time, both were checked Welwyn North area for Thameslink etc service, then no more checks to York. The tightest timed section is York-Newcastle 49 mins, which not achieve yet, then made up time Newcastle-Edinburgh. The sections were Kings Cross-York 103.41.9, York-Newcastle 53.10.8, and Newcastle Edinburgh 81.10.3 mins, giving running time of 3hrs 57. 01 mins, and overall approx 4hrs 05 mins.
Both Edinburgh-London runs struggled to keep to time, with the one i timed doing Edinburgh-Newcastle 82.13 mins, Newcastle-York 51.25 mins and York-Kings Cross 115.06 mins. I think the Dec 2025 East Coast timetable is a decent effort with good timetabling, and when service runs well, especially Kings Cross-York, theres chance of a fastest class 800 timing for London to York, though wont beat fastest 91 run, as completely different era.