When you can play a gig like this in front of Glasgow's most discerning crowd, and walk off having spectacularly won over all concerned, it's proof positive of a reputation that has endured for two and a half decades.
Given that they formed in 1980 and split in 1981 with one great album to their name, the Engines' legacy is substantial, and Franz are just one of many imitators or acknowledged fans. The quartet did re-form for the first time since 1981 to support the Mercury Music prizeholders at Glasgow's SECC in December, but it speaks volumes for their disregard for the music industry that they didn't cash in with releases and tours.
A few selective, low-key appearances later, they're telling us firmly that this will be the last date in Scotland, with their show at the ICA in London this Saturday the last ever. If that really is the intention - and not just mischief-making by the lead singer Davy Henderson - what a great place this was for the occasion - the Sub Club's Optimo night is an underground institution.
The club's founder, a DJ named Twitch, made his name with Edinburgh's techno night Pure. He's now branched out into post-punk, rock'n'roll and quirky European electro. Franz Ferdinand came to prominence on this stage in 2003.
So, in front of an expectant crowd of local scenesters, mostly in their mid-twenties, the fortysomething Henderson is wonderfully stony-faced and defiant. "Hello," he greets us, "we're from the 20th century. This is 'Plastic Gift'."
The short instrumental is a handy icebreaker for all the West End fashionistas puzzling at these four men - Henderson, the guitarist Murray Slade, the bassist Graham Main and the drummer Russell Burn - who look like they could be playing Rod Stewart covers. It's an angular, strident version of all the most forward-looking music they've heard here, and the next 45 minutes is a well-received history lesson.
A lesson, of course, where dancing is permitted, in particular to the funk-laden stamp of "Get Up and Use Me" or "Hungry Beat". Playing his solos crouched, then springing up to sing, the enigmatic Henderson tells us not to applaud because "it wasn't that good - and there's not going to be a next time". Oh, it certainly was that good...