An "anti-establishment cult" attempted to kidnap a coroner and subject him to "corporal punishment", a court heard.
Mark Christopher, 58, Matthew Martin, 47, Shiza Harper, 45, and Sean Harper, 38, wanted to "shut down" Essex Coroner's Court in April 2023, it was alleged.
They stormed into the building in Chelmsford with handcuffs as they worked to "arrest, detain and take" senior coroner Lincoln Brookes, a prosecutor said.
The defendants, from Essex and east London, deny a number of offences.
Chelmsford Crown Court heard they wanted to "ultimately incite kidnap and corporal punishment to the senior coroner".
Allister Walker, prosecuting, said it was "only by chance" that Mr Brookes was not there when they broke into courtroom two on 20 April 2023.
However, he was left in "fear and distress" upon hearing of the plot targeting him.
The court was shown footage allegedly filmed by Matthew Martin when the group entered Essex Coroner's Court
In a video played to the court, the group were seen wearing hi-vis jackets and carrying handcuffs as they entered the courtroom.
Area coroner Michelle Brown, who was in the middle of an inquest hearing at the time, could be heard saying: "Please don't resort to violence."
"Those in court were particularly alarmed by the group's actions," Mr Walker said.
'Call to arms'
The jury heard the incident followed a series of "warrants" allegedly sent to Mr Brookes by Mr Christopher.
He was said to be the "chief judge" of an online movement called the "Federal Postal Court" or the "Court of the People".
Mr Walker said the defendants had "self-conferred" legal powers and they encouraged people to pay a subscription to join them.
He said the movement had a "significant following" online and described it as an "anti-establishment protest, cult or conspiracy theory".
The group believed the senior coroner for Essex, Lincoln Brookes, was acting "unlawfully" in his role, the jury was told
Below Mr Christopher in ranking were Mr Martin and Mr Harper acting as his "sheriffs" and Ms Harper as a "postal inspector", the trial heard.
Their mission was to "close down the courts" in Essex, Mr Walker told the jury.
"Part and parcel of that was arresting, detaining and taking the coroner himself, Mr Brookes," he said.
The prosecutor said Mr Christopher had "called his followers to arms in an online rally" to support their efforts.
Upon arriving at the court last April, Mr Martin allegedly assaulted a security guard and broke his glasses.
The court heard Mr Martin was arrested at the scene, with the other defendants detained near Southend County Court.
Mr Martin and Ms Harper, who lives with Mr Harper in South Benfleet, Essex, were found to be in possession of handcuffs, the jury heard.
They believed Mr Brookes had been acting "unlawfully" and wanted to hand him over to the police, it was alleged.
The defendants all deny conspiracy to kidnap and conspiracy to commit false imprisonment.
Mr Martin, from Plaistow, east London, also denies assault by beating and criminal damage.
Mr Christopher, from Forest Gate, east London, denies a further charge of sending a letter or email with intent to cause distress of anxiety.
The trial continues.