Police were called at4.41pm on Friday, 29 January to an address in a residential block in Rinaldo Road, at the junction with Balham High Road SW12, after reports of loud music and a large number of people in attendance.
Officers attended and found 25 people in the address having a party.
The group was dispersed and all 25 were reported for the consideration of fixed penalty notices of £800 for breaking the rules designed to prevent the spread of the virus.
Inspector Sarah Burrell of the South West BCU said: “My officers should not have to be putting themselves in harm’s way by attending flagrant breaches such as this, but anyone who organises or attends such an event can be assured that we will turn up and we will issue fines.
“This was a blatant breach of the Coronavirus rules that are in place to save lives and protect the huge pressure on the NHS.
“We are still in the middle of a global pandemic and the risks are simply not worth it.”