Growing up near Skipton in the 1950s (therefore after nationalisation) the default route to London was always to St Pancras. If you wanted (and I often persuaded my parents to do this) you could ask for tickets to Kings Cross but that involved a walk (sometimes run, if the connection was tight) down the road to Leeds Central. It was still quicker (and more exciting), but only young anoraks like me bothered.
I imagine it was only after Central closed and Kings Cross trains ran into Leeds City as was, that they began to sideline the Midland route. When did that happen? I assume a few years before electrification.
Despite the few odd trains from St Pancras after 1962, as I wrote up thread, the KX route was absolutely the 'main line' by then, and I suspect even before that. By the winter timetable of 62, while you could still go via the Midland, the trains that went that way were really there to serve the East Midland and give connections to stations south of Leicester.
The Midland did run via Normanton, which is effectively suburban Wakefield, a longstanding major railway point from early railway times, with the Lancashire & Yorkshire main line coming in to finish at the west end, and the North Eastern to York at the east end. Even very early trains from Newcastle to London used to stop there at an infamous refreshment room, but since BR times it has been an unstaffed halt.
Why was it "infamous", please? As I was told, many, many years ago, all (?) the St Pancras - Scottish trains stopped there for a number of years in the 19th century to allow passengers to take a meal.
Regarding Bedford, if I am not mistaken the fast lines did not have any platforms until a few decades ago, passing just outside the west side of the station, until (seemingly grudgingly) they were added more recently. As the main Midland 4-track was operated more as Passenger and Goods, rather than Fast and Slow, the resulting need for all passenger trains to weave over and back to the station long led to a poor service there by expresses.
Yet, AFAIK, all the stations, right up to Kettering, had platforms on both fast and 'goods' lines. I'm talking about the likes of Sharnbrook and Burton Latimer, not just places like Leagrave.
By the time the Cl 45s took over, the Bedford stop was not such a problem. The hourly semi-fast service was adequate, indeed, rather marvellous in the sense that you could get from anywhere to anywhere on the system every hour, either directly or with a change at Leicester.
But in steam days, the Bedford stop must have meant quite a time penalty, not only because of the weaving onto the slows, but when starting from Bedford trains faced tough climbs almost immediately in the up direction and within four miles in the down. I doubt a stopper at Bedford could get over Sharnbrook summit at more than 45 mph with steam on down trains (open to correction - I don't think I've ever seen any logs). A Cl 45 would be doing close to 60 mph, not much difference if it had gone through Bedford on the fasts.
I do wonder if the decision not to put platforms in on the fast avoiding lines back in the 1880s (or was it 90s?) cost Bedford dearly and aided Luton as a commercial centre over the county town - not obviously, but in a slow 'drip drip' type of way over the years, because it was easier to stop expresses there if needed.