This has been filmed by different people before, located in a museum. I was in the area so it would've been rude not to check it out!
Oddly enough every other toilet (except one 80's Armitage Shanks 'Curzon' washdown) has been replaced, but thankfully this remains. It does boggle me why this was the only syphonic they installed since the Curzons seemed to have been installed at the same time. My only guess really is the cubicles are arranged around a slightly curved wall, so this being the middle has the most depth, since double trap toilets are longer.
Good flush on this and hasn't changed thankfully, a bit sluggish to start but that seems to be a theme with this generation of Unisyla. I've included a couple of takes, plus a paper flush and cistern view.