So I just watched the first part of the latest two-parter the other night. The Doppelgangers idea was pretty cool, but now that the Doctor's saying they're some enemy in the future I've been racking my brains trying to figure out who.

Funnily enough, the suits they were wearing and those helmets make me think Sontarans. This...doesn't seem like the right answer.

Also don't spoil me Europeans and others who are ahead of me.