In message , at 12:19:19 on
Sun, 17 Apr 2005, Bob Wood remarked:
I believe that the 'through the night' service to Luton Airport will
continue to leave from the St Pancras (Interim) station.

Doesn't appear as such on NRE, eg:

Outward Journey: Tuesday 24 May 2005

KINGS CROSS THAMESLINK 03:32 Train THAMESLINK RAIL
LTD.
LUTON 04:20
--
Roland Perry