The special 91 run London-Edinburgh, did York in under 97 mins, and the fastest London-York on one of the Scottish Pullmans is few secs over 97 mins, was doing around 130mph, there are logs of 135-140mph runs by 91’s, there is one i have seen which did London-Doncaster in just under 80 mins, due to fitters attention, stopped center road, then went like clappers again to York, about 138mph, if had managed clear run, no signal stop, could have done London-York in about 95 mins, and several other 135-140mph runs have been recorded, and these were done by experienced time and speed loggers, so trust there speeds and times.