The Queen and Duke of Edinburgh have visited the Old Bailey to mark the building's centenary.
The Queen unveiled a plaque
The Central Criminal Court has hosted the notorious trials of Dr Crippen, Ruth Ellis and Peter Sutcliffe.
The Queen spoke to sheriffs and judges in the courthouse's Grand Hall before unveiling a plaque.
A courthouse has stood on the site since the 17th Century, but the royal visit marked the 100-year anniversary of the present building.
The Queen was dressed in a purple jacket and skirt decorated with tiny flowers for the evening reception at the building, officially called the Central Criminal Court.
It was believed to be her first visit to the courthouse, which was opened by her great grandfather King Edward VII in 1907.
The nickname the Old Bailey comes from the street where the courthouse is located, which follows the line of the original fortified wall of the city, known as the "bailey".
The Queen chatted to archivists about the history of the building and a former judge who is 102-years-old.
She went on to unveil a large gold plaque, to be placed next to a similar one revealed by King Edward VII.
The Lord Mayor of London, John Stuttard, said the Bailey was "perhaps the most famous court in the world".
The court's most senior judge, Recorder of London Judge Peter Beaumont, earlier said the Old Bailey set a benchmark for standards of justice across the country.
"We believe this is the centre of excellence, trying as we do serious crime day in, day out," he told BBC Radio Four's Today programme.
"You have to remember that the really important decision in every criminal trial is not the judge's, but the jury's.
"The 1,200 people who come every month through our front door to work often for several months in our 18 courts [are] trying really important trials and often making very difficult decisions about other people."
The site dates back to medieval times when it was taken up by the notorious Newgate prison.
The gaol was built in 1188 and rebuilt in 1770, and was London's main prison in the early 19th Century.
Public hangings and public executions took place outside until 1868.