When is an opera not an opera? When it is The Threepenny Opera, essentially a combination of a play, a musical, a parody and a didactic exercise.

So it would not be unreasonable to suggest that the Brecht and Weill Threepenny Opera is the most ambitious production put on by OVO during its summer Roman Festival at Verulamium.

For The Threepenny Opera is so much more than the famous song Mack the Knife, beloved of fans of Sinatra and his ilk.

It is in fact comprised of a whole cast of flawed characters who demonstrate Brecht’s central theme of exposing social and monetary injustice while at the same time being highly entertaining.

Herts Advertiser: The Threepenny Opera at the Roman Theatre in St AlbansThe Threepenny Opera at the Roman Theatre in St Albans (Image: Elliott Franks)

Macheath is the central character, a notorious criminal who marries Polly Peachum, the daughter of a leader of a ring of London beggars.

But Macheath is no lovable rogue – he is an anti-hero with few if any redeeming features. And it soon becomes clear that neither do the majority of the cast.

Ironically, as it was written in the 1920s well before the Me Too movement, it is the women in Macheath’s life who play the biggest part in what should be his downfall.

As they have done throughout the festival, OVO perform Threepenny Opera on a sparse stage with the minimum of props. And it works because it mirrors the lack of morals in all the characters.

It is directed by OVO co-founder Adam Nichols with co-director Julia Mintzer, both of whom are devotees of Brecht. That may explain why there is a lot of imagery in the production that goes over the heads of many in the audience, myself included.

But it doesn’t matter because it only adds to the colour of a production that is absolutely stunning in the first act but a little tamer in the second.

Peter Watts as Macheath and Emily Panes as Polly are mesmerising throughout and both have superb singing voices. Their love song in Act One is a high spot.

They are backed by a first-rate cast, nearly all of whom double up as the orchestra so we have trombones, saxophones, a cello and more besides being played on stage.

Lada Valesova, as both musical director and conductor, is also frequently on stage, and carries off her multiple roles with aplomb.

Mark Carlisle as Jonathan Peachum is a match for Macheath in terms of moral turpitude and I loved Annette Yeo as his wife Celia – what a voice and presence!

Faith Turner as Low Dive Jenny and Emilia Harrild as Lucy Brown, both of whom have a claim on Macheath, are also excellent.

The Threepenny Opera is not a typical musical show but in terms of pure entertainment it is both thought-provoking and a joy.

It can be seen at the Roman theatre until Wednesday (6) before it transfers to Cornwall’s Minack Theatre and The Cockpit in London.