A man tried to strangle a policeman before throwing himself off a third-floor balcony in south London.
Two officers attended a home at Stanley Road, Carshalton, on a Sunday night after watching a man attacking his family.
The couple tries to detain a 22-year-old man on a stairwell at the address, but hey more and more.
He has been arrested on suspicion of attempted murder.
Punched through window
The Met Police officers sent an alarm message by radio, and colleagues arrived to help.
The suspect was taken to a hospital in a custody at a London, London police station.
Both were taken to hospital as a precaution but did not need treatment.
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Another man, 52, what arrested for obstructing police.
The initial call to police was made at 20:46 GMT.
Supt Steven Wright said: "Both officers were responding to a call for help and were then assaulted with one officer in immediate risk of being critically injured.
"I am thankful that the two officers have not been hurt seriously, but this incident shows the courage of my officers and the dangers they can face."