The police were flagged down by members of the public on Dockead in Bermondsey around 6pm on Saturday (March 15).
A man was being restrained by the public after allegedly assaulting two pensioners and another man.
The 35-year-old man was arrested on suspicion of grievous bodily harm and is in custody.
The victims, a man and woman in their 70s and a man in his 20s were hurt in the incident but there has been no update on their condition.
A Metropolitan Police spokesperson said: “At around 18:OOhrs on Saturday, 15 March, police were flagged down by members of the public in Dockhead SD.
“A man was being detained having allegedly assaulted two men and a woman.
“The man, aged 35, was arrested on suspicion of grievous bodily harm and remains in custody.
“The victims, two men in their 70s and 20s, and a woman also in her 70s, were injured – an update on their condition awaits.”
