Veggie Pret on Soho's Broadwick Street offers a range of 45 vegetarian and vegan dishes. Pret a Manger Pret a Manger's Veggie Pret pop-up opened in London on June 1, and was meant to close after a month.

But the restaurant, which serves vegetarian and vegan dishes on Soho's Broadwick Street, was such a hit that it was kept open for a further 12 weeks over the summer.

Now it's being made permanent, Pret a Manger CEO Clive Schlee announced on the company's blog on September 6.

"We were so overwhelmed by the public response that we kept it open," Schlee wrote of the vegetarian restaurant.

The company is also planning to open a second Veggie Pret in London, with hopes to open more vegetarian Pret cafes across the country.

Inside Veggie Pret. Pret a Manger

Schlee owes the success of Veggie Pret — which offers salad "superbowls," healthy smoothies, and "plant pots" with raw vegetables — to the growing trend of eating clean.

"Clearly, the move towards a plant-based diet is gathering momentum, especially among millennials," he wrote. "Many [vegetarians and vegans] have been advocating eating less meat for years and have been thrilled to see a major UK business take up the cause."

Although Pret expected its vegetarian shop sales to plummet by 30%, its sales actually grew, according to a press release from the company. Two weeks into the pop-up's opening in June, the shop reported that sales were up by 70% from the year before, when the cafe served meat.

And of the many dishes on the menu, Veggie Pret's eight best-selling items have been vegan-friendly, the press release said.

A Crunchy Raw Rainbow Superbowl — one of many "superbowls" available at Veggie Pret. Chloe Pantazi/Business Insider

"We are now debating where to open the second Veggie Pret," Schlee wrote. "The odds are that it will be a visible corner in the City of London, where we can convert an existing shop to a pop up and see if it resonates with city workers before deciding whether or not to make it permanent."

As for the rest of the country, Schlee wrote that he hopes to "bring Veggie Pret to more cities in due course."

Cambridge could be the first city outside of the capital to open a vegetarian and vegan version of the restaurant. Schlee mentioned "a well subscribed petition" to turn one of the two Pret cafes in the university city into a Veggie Pret.