What? Really? Weird?
They're 37 pattern universal aka basic pouches. They held Bren mags, hand grenades, rifle grenades, .303 bandoleers and for the Mk III pouch ONLY, Sten mags. There was also a separate Sten mag bandoleer.
Far from weird, they're seen on every rifleman's 37 pattern webbing. Also frequently with officers who didn't wish to get themselves sniped for being conspicuously armed with only a pistol. If you've seen any photo of a Commonwealth soldier with 37 pattern webbing, you've seen those pouches.