The West Coast ML to have direct service to Inverness or Aberdeen.
Was this posted in the right thread? If it was, it's not clear who you were replying to.
The West Coast ML to have direct service to Inverness or Aberdeen.
I think the OP is after the most minimum required changes. He also disregards routes involving ferry links.
But even if not, Mallaig - Shanklin, for example, can be done by changing at Glasgow (walk), London (which counts as one change) or Bristol, Portsmouth and Ryde, so four.
If you wanted a day out in Lowestoft, you could board the 17:13 service from Kyle of Lochalsh and make 7 changes arriving into Lowestoft at 11:35 and enjoy just over 7 and a half hours in Lowestoft before boarding the 19:07 service from Lowestoft and make 6 changes and arrive back at Kyle of Lochalsh less than 48 hours after departure at 16:12, But it could be done in 4 or 5 I think.
Do you mean that Glasgow QS - Glasgow Central is not allowed?
I assume from the example you just gave that is the case as otherwise you would be able to do it with 3 changes: Glasgow QS / Central, Manchester Piccadilly, Grimsby Town.
Four will take some beating, and your other question I will need to think about it. Off the top of my head, two is the most I have for Birmingham, which I assume is within your definition of "big city"?
Is there any station without a direct service to one of the central Belfast stations (I take it to mean anywhere between Great Victoria St and Central) in Northern Ireland? Do you count the Irish Republic?