The courts have fallen silent and cases were briefly brought to a halt as judges expressed their “profound sorrow” at the death of the Queen.
Lawyers and court users gathered in the Great Hall of the Old Bailey to observe the two-minute silence at 10am.
Among them were dozens of senior barristers whose titles will now change from Queen’s Counsel to King’s Counsel.
Before observing the silence, the Common Serjeant, Judge Richard Marks KC said it was a “profoundly sad occasion”.
“I’m sure we all send our very deepest condolences to members of the royal family.”
Some Old Bailey judges, who gathered in the hall, wore “mourning bands” with dark lines around their necks instead of their usual collars.
Traditionally, the garb is worn for the entire mourning period but is not obligatory.
At the end of the two-minute silence, Judge Marks said a book of condolence had been opened as well as one at the High Court.
He said it was “indeed the end of an era” and a time of “profound sorrow”, before adding: “God save the King.”
As well as “mourning bands” senior barristers and judges are permitted to wear “weepers” – large white cuffs attached to their black robes.
“Weepers” are traditionally worn as an expression of sorrow.
As members of King’s Counsel – KCs – returned to the courtroom, many of them donned the ceremonial dress.
Before the two-minute silence at the Old Bailey, the new King was acknowledged as the first case of the day was heard at 9.30am in court nine.
In a small change from the traditional announcement, a court usher solemnly declared: “Silence be upstanding in court.
“All persons who have anything to do before My Lords and Ladies, the King’s Justices at the Central Criminal Court draw near and give your attendance.”
On the roof of the historic building, the Union flag fluttered at half-mast near to the golden statue of Lady Justice set against a dark sky.
The court will not open on the day of the Queen’s funeral.
As a princess in her teens, Elizabeth visited the Old Bailey with Princess Margaret and sat in the famous Court One for an afternoon as part of her royal education.
She returned to the Central Criminal Court as Queen in 1971 for lunch with the Lord Mayor, Sheriffs and judges.
In 2007, she attended a reception to mark the centenary of the Old Bailey.
Similar respects were paid at courts around the country.
Doncaster Coroner’s Court observed two minutes’ silence at the beginning of the final day of an inquest into the death of grandmother Nargis Begum in a collision on a smart motorway.
Senior coroner Nicola Mundy addressed lawyers, family members, journalists and police officers, saying: “As you are all aware, we received the sad news that Queen Elizabeth II passed away. Before we commence proceedings today I would like to observe two minutes’ silence in her honour.”
A two-minute silence was also observed at the start of some proceedings at the Royal Courts of Justice in central London on Friday morning, including in Court 76 where judges are hearing a challenge brought over the Government’s plans to send some asylum seekers to Rwanda.
Lord Justice Lewis told a packed courtroom containing some 40 bewigged barristers shortly after 10.30am: “You will have heard, all of you, the sad news of the death yesterday of Her Majesty the Queen.
“The court will continue to sit today, but we will begin this hearing with two minutes’ silence.
“So may I ask you please to bow your heads in memory of our late sovereign?”
A sign outside Court 15, known as the Lord Chancellor’s court, earlier welcomed people in to observe a silence at 10am.
Recorder Andrew Allen KC told people inside: “Following the death of Her Majesty the Queen, His Majesty’s courts and tribunals across the country are observing a two-minute silence at the start of each court day.”
Stephen Worthington was one of the first barristers to be introduced as “KC” at a High Court hearing.
Mr Worthington appeared in at Court 13 at the Royal Courts of Justice in London.
Deputy High Court Judge Anthony Metzer oversaw a hearing involving a damages claim after a child was seriously in an accident.
The judge was told that a settlement had been reached – and said the parties involved could not identified in media reports.
A barrister representing the claimant told the judge that an agreement had been reached and said Mr Worthington “KC” was representing the defendant.
Royal Court of Justice case lists on Friday still referred to the “Queen’s Bench Division” – a division of the High Court.
Lists had been compiled before news of the Queen’s death emerged.
Meanwhile, the Criminal Bar Association announced that planned barristers’ demonstrations next week had been cancelled “out of respect”.
But the CBA said there had been “no movement” from the Government so industrial action would continue.
