Wonderful period photo, Nigel. Indeed, I remember it. I remember being brought by bus to Portmarnock in summer 1955 by my parents. We went out of a Regent double decker and came back on a Regal 3 single decker (at least I think it was, slight possibility it was a Gardner, but I don't think so. I was 5 at the time!).

Surprising to see the CIE P class bus there. Must have been private hire. CIE did not serve Portmarnock at all in those days.