Hi Nick,
It was Ofw. Ludwig Reibel of 1./J.G. 53 (38 victories). The memoirs of P/O. Robertson, shot down and wounded that day, have been posted online, here:
http://www.pprune.org/military-aviat...t-ww11-72.html. 20 December 1942 is about a third of the way down.
Cheers,
Andrew A.
Air War Publications -
www.airwarpublications.com/earticles