If you have not completed the AD story line, this may be a spoiler for you.
Those who have, you may recall that Estre had a little arrangement with Mehrunes Dagon. And, at the end of that quest you witness a conversation between Estre and Dagon. Those perceptive enough would have noticed that Malcolm McDowell did the acting for Dagon's voice.
"One simple does not...' hire the likes of Malcolm McDowel in their video game to only speak 2 or 3 lines in one quest that only a percentage of players will ever hear. Only those who complete the AD quests will hear it as it's the only time he makes an appearance so far. I'm willing to bet they have more of his work on this game already recorded for a future update release or expansion. Really... how much would that guy have charged just to speak 2 or 3 lines?
I have my Tamriel Hero title, and I did not recognize his voice in any other content. If I'm wrong and just not picking it up that he voiced other content, then close this thread. But if not, I suspect we will hear and "see" him in future content.
"There is no moisture in your angry stares." - Laughs-at-All
"I don't know why I bother guarding you horrible people." - Orama Sadas
"Scales here is about to have a really bad day..." - Valeric
"Just tell me what you're doing here before I turn your heart into a tomato..." - Sereyne
"Break those rocks! Dig those ditches! Why??? Because I want you to!!!" - Ifriz the Unraveller
"There are worse masters than I. Far worse." - Molag Bal
"I humiliated the Daedra in Mehrunes Spite." - You, when turning in a specific Undaunted Daily.
"I'm not finding you very pleasant!" - Adla the Brewer
"Old Ri'hirr likes his birds slow and stupid!" - Old Ri'hirr
"When things get dirty... Oh, I get so flustered." - Meredil the Archivist
"Too many Argonians about these days..." - Davon's Watch Guard (though I think this one has been removed from game)