Not your traditional Xmas episode

That was a slightly odd Dr. Who xmas episode - it felt like the Xmas part was grafted onto a story which otherwise had sod all to do with Christmas, and was VERY different to the usual sort of Dr. Who plot. I won't say more to avoid spoilers, but they just REALLY redefined what can exist in the Who universe, and I'm not sure it quite worked for me - it had me wondering where one of the protagonists was during every alien invasion etc. since the start of New Who!