A group who turned up at a court with handcuffs and demanded to know where the senior coroner was have been found guilty of a plot to kidnap him.

Lincoln Brookes, senior coroner for Essex, said he received a series of “very bizarre” letters in 2022 before receiving emails in April 2023 stating that “corporal punishment may be administered”.

He described the emails, which claimed to be warrants “for seizure of goods and persons”, as “troubling” and “upsetting”.

Mr Brookes told Chelmsford Crown Court that in an attachment to an email he was accused of “detrimental necromancy”.

Mark Christopher, 59, of Forest Gate, east London, Matthew Martin, 47, of Plaistow, east London, Shiza Harper, 45, of South Benfleet, Essex, and Sean Harper, 38, of South Benfleet, Essex, turned up at the coroner’s court in Chelmsford on April 20 last year.

The four defendants all denied conspiracy to kidnap and conspiracy to commit false imprisonment, but all four were found guilty on both counts by majority verdicts of 11 to one.

The verdicts of the jury followed a two-week trial at Chelmsford Crown Court and more than 10 hours of deliberation.

Christopher was also found guilty, by a unanimous verdict, of sending threatening letters to Mr Brookes with intent to cause distress or anxiety.

Mr Brookes was not in the coroner’s court building at the time of the incident last year.

Essex area coroner Michelle Brown – who had been conducting documentary inquests from paperwork and without witnesses or family present – said the group came into her courtroom.

She said the leader “kept demanding that I find and get Mr Brookes”.

The judge, Mr Justice Goss, told jurors while summing up evidence in the case that the defendants were “members of a group called the Federal Postal Court, or Court of the People”.

He said Christopher was the “self-appointed leader” with the title “chief judge of England and all dominions”.

“He trained under the late David Wynn Miller,” the judge said.

He said Martin was a “sheriff and a coroner”, Sean Harper a “sheriff” and his wife Shiza Harper a “postal inspector and auditor”.

“The other three defendants (Martin, Harper and Harper) were all qualified by him (Christopher),” the judge said.

After a few more minutes of deliberation, jurors cleared Martin of an allegation of assault by beating of security guard Eamonn McCormack on April 20 2023, and he was also found not guilty of the criminal damage of his spectacles.

The judge bailed Martin, Harper and Harper until their sentencing, which is due to take place in the week beginning September 23.

Martin said after verdicts were returned: “Thank you jury very much, I know it’s been hard for you.”

Christopher, who was in custody during the trial, was remanded in custody until his sentencing.

Detective Chief Inspector Nathan Hutchinson, of Essex Police, said afterwards: “The ideologies of this group were concerning and they genuinely believed that they had the power to construct their own legal system, threaten others and were above English law.

“No-one should feel threatened for doing their job.”

He commended workers at the coroner’s court who “acted calmly and rationally during an intimidating and traumatising ordeal”.

“It’s clear that throughout the investigation and court proceedings, that the group had no belief or regard in the British justice system,” said Mr Hutchinson.

“The investigation team, especially investigating officer Pc Thomas Berry, remained focused and committed to gather the evidence needed to convict this concerning group of people and prevent them from causing harm to anyone.”

Essex Police said that on April 12 last year they received a report of letters, dated April 6, being sent to the coroner.

“These documents were immediately assessed by a senior detective and following consultation were deemed as low risk,” a force spokesperson said.

The letters were “shared with key partners and national units including counter-terrorism police for a risk assessment”, police said.

“An intelligence report was submitted in relation to the group, in order to monitor any developments and act proportionately,” the force spokesperson said.

“The information was also added to the MP and Protected Persons Database.”

The force said investigators were “not made aware of the letter dated April 18 which detailed this group’s plans to attend court on April 20, giving officers no opportunity to proactively respond to the threats made”.