“You can’t come in here,” SevenStreets is told. “The Mersey Beatles are on – it’s tickets only.”

That’s as may be, but we’re attending a stag do and the stag and his do are all inside. The bouncer adopts a ‘tell it to the puffer jacket’ look, averts his gaze and repeats some stuff about tickets and the Mersey Beatles.

Briefly we wonder who the hell the Mersey Beatles are – and what delights await us behind a black curtain in the ambitiously titled Live Lounge. For we are in the Cavern Club (not the pub, we hasten to add and not the original Cavern Club either – that one was bulldozed decades ago and a multi-story went up on top of it).

So we watch twenty minutes of what amounts to a Beatles karaoke with a live band in the main room. The people getting up on stage are pretty good; briefly we consider getting up for a rendition of Helter Skelter.

Eventually a friendly face appears and we make our way to the hallowed Live Lounge. Enormous sculptures of John, Paul, George and Ringo (not decapitated, thankfully) adorn the wall. It’s quite hard to tell which is which.

The Live Lounge shares one key similarity – at least to the original Cavern. It’s like a steam room. A packed, energetic dance floor and an apparent lack of aircon ensures that most of the audience look like they’ve had a bucket of water thrown over them. On the stage are four mop-topped musicians wielding Sergeant Peppers outfits and fake muzzies. Needless to say the Mersey Beatles are a tribute act; our heart sinks.

It’s clear the gig is in its psychedelic stage as a number of slower Beatles favourites get a run out. George sings Something; John sings I Am The Walrus. Paul sings one of the ones that Paul did. We didn’t hear an Octopus’ Garden though.

Only John, to our eyes, particularly resembles or sounds like his Beatle. The other avatars adopt the instruments and even tics of theirs – Paul’s head wiggling and ‘Ooooh!’ facial expression present and correct – while yer actual Ringo Starr may not feel flattered by the rather larger drummer, even if he might be flattered by his drumming.

The start of A Day In The Life is quite startling in how much it sounds like the version on Sgt. Peppers, thanks to the vocals and impressive playing. These Beatles may be ersatz, but you have to hand it to them – they’re well-drilled. How many gigs might they have played? Lots more than the original Fab Four, we’d guess.

After a break they’re in collarless suits and trotting out Helps and Tickets To Ride – the switch from late Beatles to early Beatles necessitated, we suspect, by the disappearance of a keyboard player who lent a real texture to the more complex songs. They banter among one another as if they are The Beatles.

Baby boomers with their glasses and bald spots sing along – as do the various stag and hen do-s. Does anyone have quite as broad and wide a singalong back catalogue as the Beatles?

After what seems like a couple of hours it’s time for Hey Jude and a lighters in the air moment. Well, it would be – instead a sea of hands in the air and people running down their iPhone batteries to take a picture of four blokes pretending to be four other blokes.

It’s a kind of Liverpool that can be seen in TJ Hughes, at Anfield, St John’s Market and a dozen old pubs – honest working class entertainment – and life. That’s not meant to be patronising, just an acknowledgement that the Liverpool immediately outside – Matthew Street and neon and takeways; swanky bars and Hiltons; boutique hotels and Met Quarters – is very different.

It’s not subtle and it’s all rather odd in some ways. But it was a heck of gig if you could stow away your cynicism. If only they’d done Helter Skelter.