The man known as Nick whose allegations sparked a multimillion-pound police investigation into an alleged VIP abuse ring in Westminster set up an encrypted email account and posed as a fictitious witness in an attempt to corroborate his own claims, a court has heard.

Carl Beech, 51, is accused of falsely claiming he was among victims of a group of politicians and senior figures in the military and intelligence services he claimed raped and murdered boys in the 1970s and 80s.

During Scotland Yard’s £2m inquiry into the claims, Beech pretended to be a man called Fred who had witnessed the abuse and communicated with investigating officers, Newcastle crown court heard.

Beech, known widely by the pseudonym Nick, acted as a go-between for Fred and investigating officers, before the purported witness started communicating with detectives directly using a Proton email account, the court heard.

Tony Badenoch QC, prosecuting, told jurors on Wednesday: “The Metropolitan police, in trying to speak to Fred, went through Carl Beech initially. Carl Beech purported to be corresponding with another person, Fred, and ultimately Fred made some contact via email with the Metropolitan police. Or so it appeared.

“When investigations were complete by police officers, again using international cooperation, they went to the email provider. It was an encrypted email account. The encrypted email address from which Fred was corresponding had not been set up by Fred. The person behind the encrypted email account was Carl Beech.

“There is also another layer to this deceit. When the emails were coming back by way of correspondence, Fred purported to give his real name. He said that as a child he was called John, that was his real name. John is a man actually known to Carl Beech, well known to him.”

Beech denies 12 counts of perverting the course of justice from December 2012 to March 2016 and one count of fraud over a criminal compensation payout.

The charges include that he made a false allegation of witnessing the murder of a child by the former Conservative MP Harvey Proctor. Beech is also alleged to have lied about witnessing the murder of two other children.

Others he accused of abuse included the former prime minister Edward Heath, the former home secretary Leon Brittan, Field Marshal Lord Bramall and Jimmy Savile. Bramall’s wife died without knowing her husband was to face no further action, the court was told.

The court heard that the Fred Proton email account was set up on 8 April 2015, after which Beech had gone to the police with his own claims of abuse. It was subsequently discovered the account was registered to the address beechfamily1@gmail.com.

Beech forwarded an email reply purporting to be from Fred to an independent clinical psychologist, Dr Elly Hanson, who was contacting him with the police’s knowledge.

The email to Hanson in March 2015 read: “It is something that weighs heavily on my mind and I am giving a lot of thought but it is not an easy decision for me to make. Nick and I went through hell together but he’s dealt with it a lot better than I ever will. I have never talked things through with anyone except him and I need to give consideration on how things might impact the life I have made for myself.

“Nick keeps me updated on how the investigation is progressing and I need to have reassurance and trust that it’s genuine. I know Nick wants me to come forward and I need to see if I can do what he wants me to do, but also what is right for me.”

In May 2015, Fred corresponded with investigating police directly, the court heard.

Writing to detectives, he said: “I don’t doubt the commitment of you or your officers. Carl has been keeping me informed about how things are progressing. Yes I do have reservations about speaking to the police and the fact Carl has done it is good but it just makes things more difficult for me but we have been talking a lot this weekend and I agreed to contact you directly. I don’t really know what to say or do now, except to say the name I had as a child was John and I was called J a lot of the time. J.”

The court also heard how Scotland Yard officers sent emails to John to arrange a meeting with him. But in one response from “Fred”, sent on 27 May 2015, he wrote: “What’s the point? People have died, others arrested. I do not know if I can put myself through it.”

In August 2015, John told a detective in an email that he had been threatened. He wrote: “My concerns remain and increased because I have received a threat that I take seriously. I have not told Carl about this, but if they can trace me, they can trace him. That doesn’t mean I am saying no, but I am meeting Carl in a few weeks to talk things through with him and I will then contact you again. If we did meet then, yes, I would want him there. Thank you, J.”

The trial, which is expected to last up to three months, continues.