Westminster Bridge has closed on Sunday morning after a man was stabbed, with the Metropolitan Police arresting three people on suspicion of attempted murder.
The victim, who is now fighting for his life in hospital, was attacked at around 10.40am as shocked passsers-by watched in horror.
Emergency services rushed to the scene following reports of a fight and took the man with stab wounds to hospital.
Police arrested three men on suspicion of attempted murder and a fourth on suspicion of affray while two were taken to hospital for minor facial injuries.
A road closure is in place at the bridge as police investigate.