Anthony Head can’t escape his past. I know that, because when I posted a note on Facebook a few days ago that I’d be interviewing Anthony, it took less than a minute for Gina Vivinetto to respond with two words: “Ack! GILES!” I wasn’t entirely sure if that was good or bad, but when Gina subsequently promised to tell all her online friends about the interview, I concluded “Ack!” was good. For those of you who don’t know, before landing the role of King Uthur—father of Prince Arthur—on the new NBC summer drama series “Merlin,” Head portrayed Rupert Giles, the school librarian who doubled as mentor to "Buffy the Vampire Slayer." Since "Buffy" finished, he has appeared in many United Kingdom-based television productions including "Doctor Who" and the cult comedy series "Little Britain.” Anthony Head • •