I did think it would be quicker than a Rail Replacement Bus, what really surprised me is that it isn't.
It's even more of a gap if you can get people back onto the rail network in North London / South Herts. Peterborough to Potters Bar or Borehamwood can be done in about 90 minutes by coach and can get to Kings Cross or St Pancras in 20 mins. Driving from either of those to Kings Cross is the slow part.