UK quad (30 inches x 40 inches, for in-cinema display) but it seems they just made it out of two slightly different portrait posters side-by-side.

From collector's homepage:

• https://www.filmonpaper.com/posters/diva-quad-uk/

Found as I was putting together the Cinéma du Look collection:

• https://eggplant.place/collection/00cAPSvq6ZvrnCwWCZm9xZ

The portrait commercial print version (like the left side, IIRC) was popular on young people's bedroom walls in the UK in the 80s.