“They really did go well together,” said Erin Rivers after finishing off her Greggs sausage roll paired with Bollinger rosé brut champagne. “The contrast from something very carby to a very crisp drink was really nice.”

Rivers, a 22-year-old production assistant, was one of the first people to experience a Greggs champagne bar in the food hall of Newcastle’s historic department store Fenwick.

The fine-dining menu includes steak bake with peppercorn aioli; chicken bake with katsu curry sauce and pickled cucumber; and sausage, bean and cheese melt with bloody mary ketchup.

There have been a series of in-house tasting sessions, and wine experts at Fenwick insist the “rich fruit and creamy brioche notes” of the Bollinger perfectly complement the “savoury flavours” of the Greggs sausage roll.

If people really want to go for it, they can choose to have a £75 glass of Louis Roederer Cristal champagne, or a bottle at £425.

For afters, perhaps a cocktail made from yum yum and rum. “It is very, very sweet,” said one diner.

The champagne bar seats 16 people and is inspired by 1920s Paris wine bars. It follows the success of Bistro Greggs at Fenwick last year, where diners could enjoy dishes such as a Greggs Benedict or a steak bake accompanied by truffled dauphinoise potatoes and almond-garnished green beans.

People loved it, said Ian White, the head of brand at Greggs. “We were leaping into the unknown but it was fully booked out for the whole season.”

The rise and rise of the bakery chain in recent years is well documented and shows little sign of stopping. There are more than 2,500 Greggs branches across the UK, from high streets to airports to hospitals, and bosses have set their sights on there being more than 3,000. If anyone ever did feel self-conscious about being spotted in the street with a Greggs sausage roll, do they today?

“We are a brand for everyone,” said White. “If you go into our shops when they’re busy you’ll see a broad cross-section of society. You could definitely have doctors and lawyers in front of you and guys in hi-vis jackets who have just come off shift.”

That is surely the reason that Nigella Lawson will, reports suggested this week, be the new face of Greggs this Christmas. The news led one business analyst to ask: “Is the bakery now the new John Lewis?”

White could neither confirm nor deny that Lawson was onboard.

“We are always looking for innovative, fun and different ways to launch our Christmas menu so … we’ll just have to wait and see,” he said. What is important in his eyes is that Greggs don’t start taking themselves too seriously.

“We’re aware of who we are but also who we’re not,” he said. “We are there to help feed the nation at affordable prices. When we do things like the launch of the vegan sausage roll, we’re not trying to claim we are Apple.”

The Greggs champagne bar is clearly a stunt, but who cares? At a preview on Wednesday there were smiles everywhere. “It is a bit gimmicky, but it’s such a fun experience,” said Rivers. “It is definitely going to attract a lot of people, younger and older. It’s really innovative.”

• Greggs champagne bar is at Fenwick, Newcastle, 24 October-31 December.