Thanks for the update, David. Good to know the out and back journey worked.
And yes, going back to Finsbury Park before continuing to Moorgate would have worked correctly. I agree it’s a pain to have to work around the quirks, although as I’ve said earlier, Finsbury Park has special problems going back to FCC days, and the botch job is potentially as much to do with government franchise commitments not taking account of the bigger picture at the station.