Train to Edinburgh, any risk from LHR?

Ya, lots of risk mostly related to your inbound flight. Why not just book a flight to Edinburgh and come home from London. Make more sense time wise and might be cheaper. The last time we did the same route our initial flight from the US was cancelled just as the airplane lined up on the runway to take off. Our plan was to use EasyJet to Edinburgh so we lost that ticket.

You can buy an Anytime-ticket and then there is no reason to worry about delayed flights, just take the first train to Edinburgh.

The best thing to do is just buy a ticket on the next train when you get to King's Cross.

It is very unlikely that you would have to pay the full £193 anytime single. You will virtually always be able to get a last minute Advance Single (now available until minutes before departure) or the brand new Flex70 ticket.- valid on any train 70 minutes before or 70 minutes after the train booked (if you book it ahead).
Whichever of those is available, even as a turn up passenger you should pay no more than around £90.

If you booked a Flex 70 ticket for 4 hours after Heathrow arrival (so 1030) if you were on time you could catch any Edinburgh LNER train between 0930 and 1130 (the 0930, 1000, 1030, 1100 or 1130 train). Still a gamble, but a more reasonable gamble. So if the flight is on time, you can leave early. If it's a bit late you are still OK.

You are arriving into the UK the day your tour starts? Not a good idea.

You may be affected by jet lag and need some time to acclimate to the new time zone.

If your flight to London is delayed or canceled, you could miss the first evening and possibly following morning of your tour.

Try to arrive at least a day, if not two, early.

My suggestion is to book a multi-city ticket all in one reservation: Toronto to London, London to Edinburgh, London to Toronto. This way, if you are delayed, and its on one ticket, the airline is responsible to get you to Edinburgh. If bought separately, you would have to buy a new ticket.

Take the train FROM Edinburgh to London. And do it at least one day prior to your flight home.

What Frank said.

To clarify: this travel is not the same day as the tour departs but the day before. And there are only a few carriers that fly directly to Edinburgh, hence the thought about options. (We aren't young, either! But can certainly manage suitcases etc.)

I really appreciate the useful train ticket tips and info in addition to the "Two Together" rail card option since the hubster and I will be traveling.

Looking on sample dates in June a multi city/open jaw Toronto to Edinburgh/London to Toronto on either Westjet or Air Canada is less than US$100 more than flying round trip London and gives you more certainty about your EDI arrival time, then you can do the train on the way back to London. That way you can get a very good value (maybe £40 or less) train ticket EDI-LON with certainty on your timings.

Everyone--you've helped us realize that flying and then trying for a train from London adds more complexity than we need. We'll follow the direct route as recently suggested, or simply fly Toronto/LHR to Edinburgh and enjoy the train ride on the almost-last leg of our journey from Edinburgh back to London when we have no time constraints. Grateful for your help!

Have you looked at flights that go through Amsterdam? If you are not spending any time in London at the start of your trip, it makes more sense to fly to Amsterdam and then a short flight to Edinburgh. Then at the end of your tour take the train to London if you are planning to spend some time there.

Anita makes a great suggestion. I did this when flying to Aberdeen last August. The wonderful thing is that in transiting to the UK thru Amsterdam you stay in the International departures section and don’t have to go thru any Immigration/passport control. It was the easiest airport transfer I’ve ever done. In fact I had to walk further to get some lunch than the distance from arrival gate to departure gate!

Be sure when you are looking at flights that you look at “multi-city” itineraries options on your airline website and not 2 one-way tickets.

Retired.... What you did is to hijack someone else question. Generally consider to be impolite because the OP will get notice of your answers and not you. So post your questions as a new question with answers going to you and delete your questions here. Makes is easy for everyone.