More than 150 canisters of nitrous oxide, with a street value of over £2,000, were seized on the opening day of the Notting Hill Carnival.
Police confiscated the laughing gas containers in Wormington Road on Sunday (August 29).
Nitrous oxide was among a long list of formerly legal highs, also including synthetic cannabis and a raft of other drugs, to be outlawed in May.
The Met's licensing officers also seized more than 500 cans of lager being illegally sold from a wheelie bin in Westbourne Park Road.
Police arrested more than 100 people on the opening day of the Notting Hill Carnival , as five people were stabbed.