The tube can be a sweat when you arrive at Kings Cross. But probably more reliable when you return.
I believe (but would need to check this) is that if there is a tube delay outside a passenger’s control then the train company would understand and let you travel on the next train.
I know that when making connections to Advance ticketed trains by other national rail services then passengers holding through tickets are always protected.
Not so sure about the London tube, though.
East Coast fares can be great value. It depends on the route and which ticket type you book.
I agree that London-Newcastle fares are expensive. That’s because rail has the lion’s share of the market and therefore prices accordingly.
But London-Edinburgh fares are far better value because rail is up against air.
In some cases you can book a London-Edinburgh ticket for less cost than a London-Newcastle one.
East Coast’s great deal is its £229 first class return Scottish Executive ticket valid for London-Edinburgh.
It’s far cheaper than any similar first class fare on the London-Newcastle route. All you need do is book this ticket by 1800 on the day before departure. The return sector can be left open-dated and so you can use it on a ‘walk-up’ basis.
If you buy the Scottish Exec ticket from the Edinburgh end then East Coast will throw in a Zones 1 + 2 Travelcard.