A Nazi sympathiser has been found by a court to have prepared a terrorism attack on an immigration law firm after choosing them as a target after reading a Daily Mail article.

Cavan Medlock carried a Nazi flag and a knife into a London solicitors’ offices in 2020 and then launched an attack on staff.

The attack caused so much alarm that senior lawyers lobbied the then home secretary, Dame Priti Patel, to reconsider some of the language she and others were using, claiming that it was adding to tensions.

Leaders in the profession say the incident has led to continuing concern as extreme right-wing groups single out lawyers for abuse and threats.

During his police interview, Medlock said he had chosen the firm and its immigration chief as targets after they had been named in a Daily Mail article three days earlier.

The finding at Kingston Crown Court on Tuesday was not a criminal conviction – but a conclusion by a jury of factually what happened.

A trial of the facts occurs in rare circumstances when a defendant is not well enough to either admit or deny a charge, but a case needs to be concluded.

An attempt to put Medlock on trial in March was aborted after he suffered an episode of very serious mental ill health.

The jury found he had committed the acts of preparing for an act of terrorism and making threats to kill when he stormed into the offices of law firm Duncan Lewis.

A senior judge will decide on Thursday how best to manage Medlock’s detention for public protection because he is too mentally unwell to be in a prison.

That incident happened on 7 September 2020 when the then 27-year-old Medlock walked into the firm, which has a specialist immigration law team who handle some of the most complex cases in the country.

Medlock repeatedly asked to see the firm’s head of immigration law – but after about 15 minutes of waiting, he pulled out a six-inch knife and lunged at a receptionist.

The member of staff succeeded in disarming Medlock, who was ultimately overwhelmed and subdued by other staff who rushed to the scene.

Medlock then declared that he had come to kill the senior lawyer he had been asking for and used racially offensive language against other members of staff.

When one of them identified herself as Jewish, Medlock expressed support for Hitler and the Holocaust.

Police later found a Swastika flag in his bag – and his interview confirmed an ideological motive that fitted the legal definition of terrorism.

At the time Medlock was not diagnosed with any mental ill health condition and he was assessed by a nurse as fit to speak to officers.

In his police interview, he told detectives that he had wanted to stop the firm helping immigrants by taking its immigration chief captive.

He then planned to put the Nazi flag, and another relating to the US’s slave era states, in the firm’s window as a “rallying cry to other nationalists”.

“When politics fails and the people have no alternative, I think violence is the only natural progression of that thinking to get change,” he told officers, warning that there was a “white genocide” under way.

“Boris Johnson, he’s not going to do anything about mass immigration,” he said.

“How many times have the Conservatives promised to bring the immigration [level] to 100,000 a year, and failed?”

Timothy Cray KC, prosecuting, told Kingston Crown Court: “He was admitting carrying out acts of preparation for terrorism. His brand of terrorism was clear.

“By his own admission, at the time of the attacks, he identified as a Nazi. We say that plan was designed to intimidate a section of the public.

“Can you imagine the [media] coverage? A solicitor held hostage, or perhaps worse, and the Nazi flag flying in London.

“Perhaps we can console ourselves with the fact that he would not have had many takers.”

During his police interview, Medlock said he had chosen the firm and its immigration chief as targets after they had been named in a Daily Mail article three days earlier.

“I first saw his name on [The] Daily Mail, a couple of days ago,” said Medlock.

“And then when I Googled his name and I found out he has his office right here… I was like, you know, these people, they can’t just continue to flood Europe with people nobody wants here and get away with it.”

Medlock’s phone history confirmed he had read the article which referred to “UK lawyers who coach asylum seekers” to avoid deportation.

That article came after sources in Boris Johnson’s government had been briefing some journalists for weeks that “activist lawyers” had been holding up some deportations, the court heard.

The phrase was used publicly a week before the attack in a video posted on the Home Office’s account on Twitter, now known as X.

The department’s top civil servant then banned it from the government’s PR releases.

But Dame Priti Patel, then home secretary, used the phrase in her own tweet the day before the Mail’s article – but she did not publicly mention Duncan Lewis or any other firm.

The Bar Council, the professional body for barristers in England and Wales, condemned the language and at the time called on her and Boris Johnson to “stop deliberately inflammatory language towards a profession simply doing its job”.

Mr Johnson had made separate comments deriding human rights lawyers in his October 2020 party conference speech, but did not refer to Duncan Lewis or immigration cases.

Sam Townend KC, the council’s current president, said that it had continued to warn of anti-lawyer rhetoric and it hoped a page had now been turned – but the profession’s concerns remain exceptionally high.

Richard Atkinson, the president of the Law Society, which represents solicitors, said: “The attack on Duncan Lewis solicitors was the first example of a worrying new trend.

“This eventually led to threatened attacks on 39 law firms and advice agencies during this summer’s riots.

“Many lawyers have faced deaths threats and have had to seek police protection. Until recently, this was unheard of in our country.

“This trend did not emerge from nowhere. It was closely associated with a degraded debate led by senior parliamentarians and sections of the media, largely focused on the immigration and asylum system.

“Words have consequences, particularly when they come from people in positions of seniority and power. They can legitimise hate, encourage division, and have serious repercussions.”

Dame Priti Patel has been contacted for comment.