Police are investigating after the death of a man in custody at Westminster Magistrates' Court.
The defendant, who was in his 60s, was found unresponsive in his cell on Wednesday afternoon, Her Majesty's Court And Tribunals Service said.
"Despite attempts to resuscitate him, paramedics pronounced him dead a short time later," a spokeswoman said.
"This matter is being investigated by the police therefore it would be inappropriate to comment further at this stage."
The Metropolitan Police said they were treating the death as "unexplained" after officers were called to the building in Marylebone Street, central London, shortly after 4.20pm.
The man has not been formally identified and a post-mortem examination is due to take place.
The Met's directorate of professional standards has been notified of the death.