King's Cross Thameslink was originally the Metropolitan Railway's King's Cross station (known as King's Cross Met), originally 2 platforms, until 2 more added for the 'Widened Lines' in 1868. Under the LPTB, the new platforms for their services were built further west, integrated into the Underground station, replacing use of the King's Cross Met station. But post war King's Cross Met reopened for LMSR and LNER trains through to Moorgate via the Widened Lines (had been suspended due to bomb damage).When York Road and the northbound suburban platform were in use, did GN or Midland or both trains also stop at what later became Kings Cross Thameslink? I believe this started out as a four-platform station but the Underground stopped calling when the current platforms further west were opened in around 1940.
My understanding is that trains to/from Midland always stopped at King's Cross Met; trains to/from the GN not always - in 1947 up trains did (after also calling at York Road (King's Cross) - as it was in the timetable), but down trains did not - I suspect it varied over the years.