As you walk into the Rosemary Branch, it feels like any other smart North London pub, with a mouthwatering menu at eyewatering prices served in an atmosphere of mannered, steely cool: but upstairs hides a magical surprise. An extra, private bar and tiny secret theatre over the top of the pub welcomes genuine creative risk-takers, whether performer or spectator, into another world altogether. Escaping up the narrow stairs, we find ourselves in a completely different atmosphere: warm with friendliness, quietly fizzing with expectation, not immune to a nervous giggle or two. Because, with Waste Paper Opera’s Whole Punch, you never quite know what’s going to happen next.

The word eclectic, so often misused, at last gets some real-world rehabilitation in this genuinely exciting, surprising and thoughtful evening of music, theatre and comedy. With a bewildering array of talent on offer, some of it operatic, some of it crossover, and some of it entirely other, this is a postmodern cabaret for intellectually adventurous grownups – world-weary and playful, gentle and disturbing by turns, always pushing for the highest of performance standards, and happy to take risks on the way. Even the Open Mike slot turned out to be jaw-droppingly astonishing (Francis Thompson’s The Hound of Heaven performed in calm cascades of memory, rolling wineglass in hand, by Ari: quite the party trick).

Despite its remarkably varied programme, Whole Punch still feels coherent, thanks largely to Waste Paper Opera’s particular company aesthetic which mixes up a generous dash of surrealism, a large shot of postmodern Commedia dell’arte, and direct humour with music-making of the highest quality. Their previous operas in their current series God’s Funeral & a Nightingale (The Remarkable Rocket and ‘i’ – the Opera) set a quirky tone which Whole Punch somehow maintains. A certain tension on stage holds our focus from one act to the next, however divergent.

March’s edition of Whole Punch began in the bar with Josh Herring and Daniel Thompson, accompanying themselves with piano and recorder, singing songs with evocative, unpretentious musicality to the audience as they drifted in. Pieces ranged from period folk tunes (“I will give my love an apple” – with apples presented gravely to each girl in the audience) to an Italian canzone about a donkey, complete with hee-haw chorus, You’ll Never Walk Alone (audience participation encouraged) and one of Herring’s own witty compositions about loneliness and house-parties. Non-sequiturs became the rule as we moved into the theatre for Andrew Hamilton’s The Spirit of Art, performed by Danny Saleeb and James Oldham, a defiantly post-modern piece which repeatedly layers and breaks up the phrases “I’m the Spirit of Art, and I should be listened to; I’m sorry: Art is dead; Long live…” This was followed by James Oldham as Clint, our host for the evening, disco dancing in a shimmering sequinned jacket with an air of a ringmaster. Next up was a lewd yet lovable dwarf from Paddy Waters, hovering between comedy and something altogether darker.

Caroline Kennedy’s luscious operatic soprano came into thrilling comic use in her two songs dealing with lovelife trauma, updating a classic aria with new words for the Bridget Jones generation (“Oh you arsehole, how I suffer! Only Cadbury’s brings me peace…”), or dissecting Blues anthem “Cry me a river” in heartbroken asides suffused with down-to-earth practicality. Kennedy’s natural, confessional style was utterly captivating, while her inherent comic instincts, as she grudgingly offered “just one” precious Chocolate Button to someone sitting in the front row, turned each piece from a song-with-additions into a fully rounded narrative moment – conveyed through both fine acting and Kennedy’s agile, expressive soprano.

Izzy Tennant followed as Isobel Yon, dressed in an amazing silver costume faintly reminiscent of a lobster, singing a Slavic-sounding paean of deep grief in a rich, dusky mezzo which then morphed impossibly into “Somewhere Over the Rainbow”. I couldn’t stop thinking about Lewis Carroll’s weeping lobster in The Walrus and the Carpenter; Isobel Yon was brilliantly, transcendently weird.

Next came some pleasing musical standup from Ben Kane as The Bank Accounts, an imaginary band with just one member we could see, with a song suspicious about the fashionableness of owls. James Oldham, Paddy Waters, Izzy Tennant and a member of the audience gathered on stage to perform Genevieve Murphy’s The Stroop Test, a spoken word aural sculpture about colours based on a test for ADHD. Next came gently unhinged standup from Oliver Noakes, delivered with conviction and nicely restrained pacing. Delea Shand’s opera crossover piece about Mozart’s Queen of the Night built further on Caroline Kennedy’s deconstructed-aria concept, explaining the Queen’s dark motivations in the light of her role in The Magic Flute as a protective mother by inserting powerfully feminist asides between sung passages of her eponymous aria, with Shand accompanying herself on the accordion. This might sound complicated, but in practice it flowed with direct immediacy. Shand drew connections between the Queen’s maternal anger, and her most punishing notes, which made natural comic sense of the aria’s unique musical structure – brilliantly memorable.

“Tom and Simon’s Mood Board” was probably the most experimental piece of all, with actors Tom Blake and Simon Brown creating two surrealist dramatic scenes on stage, finding comedy mainly in the process of their creation. Zany, even silly at times, Tom Blake’s childish, conspiratorial grin kept us in the palm of his hand from beginning to end as the scenarios became ever more openly unreal.

We lingered in the bar afterwards to listen to Ben Kane performing with a guitar in his guise as The Bank Accounts; if you stood still, you were passed a percussion instrument. “Next – shall we sing Coldplay’s Yellow?” Ben asked. Well; it’s the kind of night where you find you just can’t say no to anything…

• Rating: Four
• Reviewed at the Rosemary Branch Theatre on Wednesday 14 March 2018
• Presented by The Waste Paper Opera Company
• Whole Punch next comes to the Rosemary Branch on 11 April, and monthly thereafter until July
• Please note: lineups will constantly change to showcase a rolling roster of new talent