The museum that will never sleep is to put a rediscovered temperance hub at its heart.

A 19th-century cocoa room installed to lure workers away from breakfast bottles of ale has been found on the site of the new Museum of London at Smithfield meat market. The Lockhart Cocoa Room, complete with temperance meeting room on the first floor, will now be incorporated into an entrance to the £337 million complex.

Paul Williams, whose practice Stanton Williams Architects has drawn up the plan for the site, said the rooms had been boarded up.

“When the boards were taken away this revelation suddenly appeared,” he said. “There were these rather remarkable Victorian tiles which the Victoria & Albert Museum were called in to examine.”

He said the building had contained a cocoa room on the ground floor, a temperance meeting room on the first floor and a kitchen on top. “They were trying to combat drinking among the market traders,” Mr Williams added. “So we are going to restore this and it is going to become a café.”

There is a history of early-morning drinking at Smithfield, as with other all-night markets. Two pubs continue to open at a time that, for most, is set aside for breakfast.

The granting of planning permission by the City of London corporation last week is a major step for what the museum hopes will be a “world-class 24-hour destination” in what many hope will be the cultural regeneration project of the decade.

Its current home, on the Barbican estate, is due to become a concert hall for the London Symphony Orchestra.

The museum’s director, Sharon Ament, has said that she wants people on their way to work, or on their way home, at 7am to “filter through” the new museum when it opens in 2024.

Mr Williams said the site was “steeped in history and surrounded by notorious events”.

“You have stairs that take you through the sedimentary layers of the past and you are standing on the same ground that the first Roman settlements were,” he said. “If that doesn’t make your hair stand up, what does? It is a remarkable and unparalleled series of spaces.”