If you’re hoping for a mash-up of Glee with The Sound of Music, Our Ladies of Perpetual Succour may leave you praying in vain for an interval to make a polite escape.

But for fans of gross out humour and constant swearing, with a hole in their lives where an ELO jukebox musical should be, the National Theatre of Scotland’s guest appearance at the National Theatre in London will be a riotous night out.

So, the girls of the Covent school of Our Lady of Perpetual Succour, from the wilds of Oban, are on a trip to Edinburgh for a singing competition but sex and alcohol -“going mental”- are on their minds not scooping first prize. That’s a pity because their singing is really very good.

The music is undoubtedly the highlight if a slight puzzle, beautiful choral singing interspersed with — the hits of the Electric Light Orchestra.

Now I like ELO as much as any girl from the Midlands, possibly more, given a fondness for Xanadu: radiant Muse descends from Olympus to inspire a young man to open a roller disco, to a soundtrack provided, of course, by ELO. But even so, it could be argued that this production may have erred on the side of too much ELO.

Some people laughed a lot, loudly enough for me to still be able to hear them during the sperm jokes even though I had my fingers in my ears so I couldn’t hear the jokes in detail- something about submariners and, yuck, make them stop!

Some audience members really looked very uncomfortable indeed and didn’t laugh very much at all.

There is definite humour in the incongruity of the angelically beautiful sound that comes from the girls mouths when they are singing as a choir and the scatological torrent when they speak.

The show was a big hit at Edinburgh last year and has an impressive pedigree, being the work of Billy Eliot writer Lee Hall, and to be fair the production photos and National trails do include the phrase “raucously rude”. Believe them on that.

Billy Elliot — also very rude and foul-mouthed — spoke truths about pain, loss, yearning and the destruction of a community but the series of spotlight moments for each girl in Our Ladies lacked any real emotion.

The absence of a sense of time — hits from 70s/80s band ELO yet talk of CDs and the girls clearly have enough money to binge drink in bars not a well known feature of recession hit Britain though sadly prevalent now — is also a weakness.

The acting, singing and production are impeccable but the 1 hour 45 minutes straight through felt very long to me.

Responses to shows are notoriously subjective and going to Our Ladies the day after my own Convent School reunion, meant I was inevitably expecting moments where I could exchange wry smiles of recognition with other former Convent School girls; I had, in fact, brought two others along with me for just that purpose.

But, even though we had been at three different Convent schools, we felt no shared experience with the girls of Our Lady’s – and, can I just ask someone, is magic mushroom beer actually a thing anyway?

It’s not that we were all exactly angels at my school. I remember one girl taking her school hat off on the bus, which was really, really against the rules and I, personally, got a Bad Conduct mark for going on the main lawn in my indoor shoes. Talk about going mental.   6/10