A machete-wielding man was Tasered on a railway station platform as “terrified” rush hour commuters looked on.
Police pinned the man – filmed waving a “massive” blade at Tulse Hill station in South London – to the ground shortly after 18:30 GMT on Monday.
Witnesses described “chaos” as he chased people with the weapon.
A 59-year-old man was arrested on suspicion of attempted murder and possessing an offensive weapon, police said.
One witness @Vikjas85 tweeted: “Man at Tulse Hill Station with a massive machete just been Tasered by the police.”
BTP said there were no reported injuries and the incident was not believed to be terror-related.
The arrest comes on the day Sadiq Khan announced Lambeth Council leader Lib Peck as the director of his new Violence Reduction Unit.