The new Leeds bar - Assembly Underground - with 50 kinds of beer

That’s the total number of draught beers which are being served at this fabulous new bar beneath the grand stone colonnaded building at the corner of Calverley and Great George Streets. The last time I was down here, this was Carpe Diem, a long narrow bar of no particular merit except that it sometimes afforded me the chance to squirrel myself away for a liquid lunch while watching the cricket.

It lay empty and unloved for about four years before being brought back to life by Hebden Bridge's fantastic craft brewery Vocation, towards the end of last year. And its opening marked the end of a nine-month refit during which the floor area has practically doubled, with the space which was once occupied by kitchens and offices now re-invented as a bar area where those 50 beers are dispensed by a long line of chrome taps set directly into the back wall.

Blackboards above the counter and clipboards on each table detail this ever-changing wealth of choice, which includes a host of beers from around the UK and overseas. “We go for beers that you won’t find anywhere else,” says Duty Manager Jessica Parkinson joining me for a drink, though perhaps anticipating a busy day she’s drinking Red Bull rather than beer.

Instead I’ve gone for one of the 19 Vocation beers, a pint of the crisp and tropical citrus Heart and Soul (4.4% ABV), one of the entry-level products of a brewery whose fabulous range here spirals upwards towards the hearty, sweetish Breakfast Club (6.9%) which is sold in two-thirds pint Schooners.

Jessica arrived here after a spell with the excellent Market Town Taverns group, working at their chain of bars – The Mews in Wetherby, Horse and Farrier in Otley and East of Arcadia in Meanwood: “I wanted to do something different, and Vocation was already my favourite brewery. They’ve created a bar similar to Belgrave, North Bar and Northern Monk, which brings the best of these together in one place.”

Its winning combination of quality craft ale, interesting food, and a lively, funky hipster atmosphere is one which would be familiar to all who have visited this trinity of great city bars.

Stepping down a short flight of steps from Great George Street, you enter a cavernous main room of long wooden tables and benches, where a street food vibe meets the industrial chic of bare red brick and exposed wiring, something of a contrast to the grand Grade II listed Victorian stone outside.

It’s almost underground, but not quite. Arched windows allow some sunlight to trickle in from Great George Street and Millennium Square; the wheels of cars and the feet of shoppers pass by at eye level.

Along the walls, a series of kiosks has been given over to vendors serving a range of foods – Punjabi curries, falafels, Brazilian barbecued meats and breads, chunky burgers and fries – and more. Beyond the bar, ovens fire out pizzas with names seemingly inspired by American law and order – The Mob, The Chief and Patrol.

“We get a lot of office staff at lunchtimes,” says Jessica. “If people can’t agree on what to have for lunch, this means they can all order something different.”

A further area is given over to the Staff Room, Assembly’s cocktail bar, which has helped to establish this subterranean haunt on the city’s nightlife circuit.