A mum-of-two was found dead by a team of police officers who smashed their way through the front door, according to neighbours.
An hour earlier her two boys, aged seven and ten, and their father, 57, were discovered at the foot of Beachy Head in East Sussex.
Shortly after 6pm on Monday evening police were called to the house in Twickenham, south west London, and discovered the mum alone with multiple stab wounds.
A Metropolitan Police spokesman said:
No arrests have been made and the Met said officers are not looking for anyone else in connection with the investigation.
The London home - which neighbours believe was rented - remained sealed off with police tape and had a significant police presence outside on Tuesday afternoon. Officers in forensic uniforms were seen inspecting the front garden and bins.