The victim has been named by detectives as 30-year-old Takieddine Boudhane.
The Metropolitan Police confirmed they were called to the Whitehall building at 1.06pm on Thursday following reports of a stabbing.
Police were called at 12.13pm on Saturday to a residential road in Enfield.
Two teenagers were stabbed in Hackney and one man in Camden in the same night.
A woman is in hospital after being stabbed in an attack in north London, police have said.
The stabbing was a “vicious and unwarranted attack on a completely innocent man”, police say.
A 29 year-old man has died from stab wounds after reports of a fight in Gowan Road.
The teenage male was found with stab wounds to his chest in Kensington and was taken to hospital where he died a short time after.
The boy was found injured in Deedmore Road, Coventry, shortly before midnight on Saturday and died later in hospital.
The incident comes amid heightened concern over violent crime in the capital.