Are there fast trains from London to Glasgow?

Not sure what you mean by the phrase -- fast train. They are all pretty fast but they do make a number of stops. We took the train from Edinburgh to London. Very pleasant and fairly quick in the range of 5 hours. Doubt if you could fly any quicker.

According to Via Michelin, the fastest route from London to Glasgow by car takes just over 7 hours if you drive straight through, ie, no stops for food or toilets. London to Edinburgh takes almost a half hour longer.

thank you all for your help!

Train guru The Man In Seat 61 is London based, so he has lots of information about travel in the UK by train. Here's his general UK page: https://www.seat61.com/UK-train-travel.htm

and here's his London to Edinburgh page, complete with lots of photos of every step of the journey: https://www.seat61.com/london-to-edinburgh-by-train.htm

I also agree that train is by far the fastest way between these cities door to door. Unless you're already at an airport, that is.

I understand the desire to break a trip up into topics posted separately, but then the big picture is lost. Just confirm that between Scotland and Provence that you actually want to visit London, otherwise fly from Scotland.

We are going on a British Isles cruise for a week. Then we had planned to go to Provence. However, we have changed our mind and decided to take extra time to go the Highlands of Scotland instead.
Amie