doctorwho:

SciFiNow:What is a typical day of shooting like?

Barnaby Edwards: On a full Dalek day you’re in there the whole day; you’re allowed out every now and then for water and a comfort break, but I’ll be inside for eight hours; something like that. Nick Briggs will be on the side of the set voicing the Dalek, and there’s a radio feed from his microphone into the Dalek with speakers positioned around the set so the actors can hear the lines. Effectively, if you go onto the set of Doctor Who, the Daleks are there; they’re real, they’re live.

Read the entire interview here. (h/t Anglophenia)

I always thought they were remote operated O.O