Annunciation, by Fra Angelico 

Hello Sheila, thanks for your message. I have also thought about the tradition of Gabriel being in the left. I don’t think there’s any theological or biblical reason for this. I like this explanation www.arts.magic-nation.co.uk/annunciation7.htm The idea that pictorial narrative is often left to right (Gabriel speaks first to announce the news to Mary) is interesting but not always the case as in Masaccio’s Tribute Money. Hope all well with you.