They aren't actual 'Brens' but Czechicon made trials guns. Note the raked rearwards backsight aperture that doesn't extend to the back of the body as the Bren does. Also vents in the muzzles that caused dust and crap when fired from off the tripod (or over low cover).

Files and folders of all the trials guns are held at the Small Arms School and are awaiting publication. Alas it's a looooooong time coming. The Small Arms School archive is packed away awaiting redevelopment of the Warminster HQ site.

Cant get the film to run. Any reason?