Police raided a baby shower attended by 20 people of widely different ages and from different households.
Body-worn footage of officers entering the house in Hornchurch, east London, on Sunday shows the group sitting around a table covered with food and a balloon arch at one end of the room.
The two organisers, men aged 22 and 44, were both reported for breaking lockdown rules.
They both face a £200 fine each.
Chief Superintendent Stephen Clayman, from the Met's East Area Basic Command Unit, said: "This gathering had people of widely different ages and from different households present.
"Whilst I fully understand that people want to get together to celebrate events, this is definitely not the time to do it in person.
"A gathering like this can have tragic consequences for all those involved and risks spreading this terrible virus to our loved ones and the wider community.
"Please have no doubt, we are determined to deal robustly with those who breach the Covid regulations in this way."
While some important events, such as funerals, can be attended by as many as 30 people during the lockdown, baby showers are not placed under such excemptions.
Most gatherings indoors of people from different households are banned under coronavirus restrictions.
Elsewhere, police in Hampshire blocked off a car park to catch and fine 26 people for gathering for a car meet in breach of Covid-19 regulations.
Officers shut off the car park at Blacknest Industrial Estate in Alton on Saturday evening after finding a large number of vehicles.
Drivers had brought their BMWs, Nissans and Toyotas from as far afield as Shropshire, Kent, Surrey and Berkshire for the event, according to Hampshire Police.
A force spokesman said that people inside the cars were from different households with many not wearing face coverings.
Superintendent Phil Lamb said: "Some of those people that officers spoke to accepted personal responsibility, but others were extremely defensive.
"It's shocking that such a large number of people have completely ignored the current lockdown, thereby putting themselves and their loved ones at risk from the virus.
"It's reckless actions like this that place increased and unnecessary pressure on the NHS."
Police in Hampshire also attended a "hot tub" party at a property in Gosport on Sunday where one of the occupants claimed to be unaware of the pandemic.
Gosport police posted on Facebook : "REPORTED! Last night persons were reported for breaching COVID-19 regulations, after holding a hot tub party in the back garden.
"One occupant claimed they were unaware of the global pandemic, and he was almost arrested after refusing to provide his details #WeAreInThisTogether."
