Same thing happens at the end of January. On the weekend of 25/26th. major work is taking place on the ECML which will be closed between London and Peterborough. EMR are warning their services will be busier than usual and wont be calling at Bedford, Luton or Luton Airport P/way, presumably to create more seats for LNER passengers.
However, the 2002 EMR service from St. Pancras on Saturday 25th, which normally runs to Leeds will be terminating at Sheffield.
It's not the first time this has happened and it's quite unfathomable to me.