The Old Bailey is to remain closed on Thursday while it undergoes “emergency repairs” after a fire.
Around 1,500 people were reportedly evacuated from the historic court house after an electrical fire on Wednesday.
A loud bang was heard and black acrid smoke billowed from an electrical substation near the rear of the building on Warwick Lane in central London.
Inside the Old Bailey, lights flickered and dimmed, and some of the 18 courtrooms suddenly descended into complete darkness just as cases were getting under way shortly after 10am.
Jurors, judges, court staff, journalists and lawyers were immediately evacuated from the front of the building.
Dozens of barristers in their black gowns and wigs lined the street as four fire engines arrived.
Around 25 firefighters were called to the scene of the fire at the rear of the building.
Later, defendants were seen being escorted by police and walked out of a side exit and into waiting prison vans to be returned to prison.
The Recorder of London, Judge Mark Lucraft KC, was seen liaising with court staff and firefighters who had entered the Old Bailey and gathered around Warwick Lane.
Barristers and other court users were told by security officials that they would not be allowed to go back inside to collect their belongings until safety checks had been carried out.
It was later confirmed that the building would remain closed on Thursday for emergency work to be carried out in the hope of reopening on Friday.
London Fire Brigade said: “Four fire engines and around 25 firefighters responded to an incident involving an electrical substation on Warwick Lane, near the rear of the Old Bailey.
“Firefighters worked with UK Power Networks to make the scene safe and bring the fire under control. The ground floor substation was partly damaged in the incident.
“Around 1,500 people were evacuated from the Old Bailey and surrounding area, and there are no reports of any injuries.
“The brigade received the first of six calls reporting the incident at 10.44am, and crews had the fire under control by 2.07pm. Firefighters from Dowgate, Soho and Dockhead Fire Station attended the scene.
“The cause of the fire is under investigation.”
Temporary chief inspector Tom Fisher, of City of London Police, said: “There is no indication at this stage that this is anything other than an incident involving an electrical sub station.
“London Fire Brigade reported that around 1,500 people were evacuated from the Old Bailey and surrounding area.”
Hundreds of people, including jurors, defendants and lawyers, pass through the Old Bailey every day. There are 18 courtrooms in operation, hearing major cases including murder and terrorism.
Among the high-profile trials abandoned for the day was that of wealthy aristocrat Constance Marten and her partner, Mark Gordon, who are accused of the manslaughter of their newborn baby daughter.
