Weddings are currently supposed to take place only under "exceptional circumstances".

However, officers found hundreds of people gathering in Stamford Hill, in north London, with the windows covered to stop people seeing inside.

The organiser of the wedding could be fined up to 10,000 pounds ($A17,700) and five others were issued 200-pound penalties.

"This was a completely unacceptable breach of the law," Detective Chief Superintendent Marcus Barnett said.

"People across the country are making sacrifices by cancelling or postponing weddings and other celebrations and there is no excuse for this type of behaviour."

The wedding took place at the Yesodey Hatorah Girls School, which serves Haredi Jewish families in the area, home to the biggest Orthodox Jewish community in Europe.

"We are absolutely horrified about last night's event and condemn it in the strongest possible terms," the school said in a statement.

An outside organisation was responsible for letting out its hall and it had no knowledge of the wedding, the school said.

Coronavirus cases soared in the UK at the end of last year after the outbreak of a new, more contagious variant of the virus, which has led to the imposition of lockdowns across the country.

Australian Associated Press