Well, this was the year after Angela hosted the 1977 Eurovision Song Contest - so maybe that's where the idea sprung from. Remember, in those days the host had to present in both English and French.
Question though - Was the programme directed from a2 (now France dot 2) in Paris, or from a gallery at TVC using an English and French speaking director? There's a couple of visible sync rolls at the top of some reports, which makes me think it probably was all run from Paris.
PPd'A's earpiece also looks very non uk standard at the time.
My user name might look like Hatton Cross, but it's pronounced Throatwobbler Mangrove.