Q. Dear Oracle
I saw a video of Will singing and also saw him singing in concert and I was wondering what song it was.

I will assume that it was Death Will Never Conquer as it's been a regular fixture on the Viva tour with Will taking lead vocal. At Christmas he also sang The Pogues (featuring Kirsty MacColl) song Fairytale of New York, so if isn't the former, it'll most likely be the latter.