Alistair indicated that he did not believe lyrium was needed for Templar abilities. If I recall Alistair thought that lyrium enhanced abilities. Alistair used his Templar skills without lyrium.
I think however there was some talk about the developers indicating that Alistairs assertions were wrong. Does anyone have the link?
Ok, I've checked the comics again, and he doesn't say anything about lyrium. He uses some templar trick on Aurelian Titus, and Isabela asks him what it was, and he says: "I used to be a templar -- fighting mages is what we do. After the Tellari swamps, I thought I'd get back in practice." Is there anything else?
I was told he said he had to take lyrium again. Sorry for yen confusion. Though as Lola said, Gaider confirmed himself how lyrium works and that Alistair took it before.
Yeah, the primary source of this DG, Thedas UK interview:
"Even if Templar magic was recognized as spellcasting, it's not innate to the Templars, if they just stopped taking lyrium eventually they would lose the ability. Although as Alistair proves, they can use the ability for a long time afterwards. I think part of that was just the requirements of gameplay, for us to have a specialization as well, so some of that story doesn't quite match up with the gameplay, and I think eventually we'd like to work the lyrium requirement back into the gameplay as well. "
It's also possible that the longer a templar takes lyrium, the more he/she needs to take it to experience the same effects. It might be that as a young templar who hadn't been taking lyrium for long, Cullen was better able to do without it. After many more years taking it, he may have become more dependent.
This is indeed how it was originally supposed to work.