Five teenagers were arrested, and five knives were seized at Clapham Junction station during Operation Sceptre, a week-long nationwide operation targeting knife crime.
Officers chased the group after they witnessed a knife being dropped and picked back up on Friday 20 May.
The arrests join dozens of other arrests, searches, and drug and weapon seizures throughout the week at stations and on-board trains throughout England, Wales and Scotland.
Similar to the operation at Clapham Junction, British Transport Police flooded the railway, often working alongside other police forces, using police dogs, plain clothed officers and knife arches to find offenders.
In total, 42 people were arrested during BTP operations. There were also 33 drug seizures, 18 weapons were seized and there were 38 weapon sweeps at stations.
Across London and the South East, the BTP Operational Support Unit and the Violent Crime Taskforce were significantly involved in the week of action, carrying out warrants at addresses and leading operations with specialist resources.
They were joined by BTP’s County Lines Taskforce.
Other notable arrests during the week include two arrested in connection with the robbery of three students in Year 7 at Coombe Lane tram stop in Croydon.
Two were arrested at Tottenham Hale station in North London for being concerns in the supply of drugs and money laundering.
Superintendent Mark Lawrie, commander for operations and proactive crime in London and the Southeast said: “Year-round we target the carrying of knives on the railway.
“In these highly proactive, regular operations, often led by our Violent Crime Taskforce, we’re targeting the carrying of any offensive weapon, whether it be with the intention to cause harm or more commonly as a misguided means of protection.
“Our first goal is ensuring passengers and railway staff are free to travel in safety and security, our second is making it undoubtedly clear there are significant consequences to carrying weapons on the railway.
“In Operation Sceptre, our officers have worked tirelessly to coordinate our resources with other police forces nationwide, working together across towns, cities and railway links to remove weapons.”