The trustees of Borough Market have used powers derived from legislation passed when George IV was on the throne to require traders and shoppers to wear face coverings and prevent takeaway food from being consumed on market premises.
Being partly outdoors, the market isn't covered by the national requirement to wear face coverings inside shops during the COVID-19 crisis.
Anyone who fails to heed requests from market officials to wear a face covering could face a £50 fine, enforceable under the market bylaws.
Adrian Bunnis, chair of the market's trustees, said: "Keeping our shopping community and our traders as safe as possible has to be our top priority.
"We have encouraged the wearing of face masks since the first lockdown. We have now decided to enforce it through our by-laws in the knowledge that the vast majority of our customers will support this.
"With London being the epicentre of the new coronavirus variant, we feel we have a duty to the community to do this so they can shop in confidence."
Access to the market will be restricted, with a one-way-system in operation. Security staff will carry out checks at the access points and help ensure social distancing is place.
The moves have been made under powers given to the market's trustees under the Borough Market (Southwark) Act 1829.
Consumption of food and drink will now also be prohibited in the market area under the same bylaws.
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