MI5 uncovers deadly plot to kill Chechnya's Laurence Olivier

A dramatic plot to assassinate a Russian politician on the streets of London has been uncovered by MI5.

The security services have issued an unprecedented public warning that Akhmed Zakayev - an exile who is a friend of Vanessa Redgrave, the actress - is the target of a murder plot.

On their advice, the Home Secretary has fought a court battle to remove the man MI5 believe would organise the "hit", who they say is a danger to "national security".

But The Sunday Telegraph can disclose that judges have allowed him to stay in Britain and fight to remain here.

The case raises serious questions about how Britain can be protected from foreign threats.

The murder plot is disclosed in the wake of the attempted assassination of German Gorbuntsov, the wealthy Russian banker shot outside his London flat and who remains seriously ill in hospital. He is believed to have been targeted by enemies he made in Russia and Moldova.

And it comes amid growing concern among the security services over the number of Russians in Britain who could present a danger to security, particularly with the London Olympics, identified as the biggest single target for terrorists in British history, fast approaching.

The assassination plot was outlined in court papers seen by this newspaper.

They reveal that the target is Zakayev, a dissident politician who lives in this country after being granted asylum. He was a politician in Chechnya, the breakaway Russian republic that has been the scene of a vicious civil war, until fleeing to London in 2002.

MI5 believes that Ramzan Kadyrov, the prime minister of Chechnya and his bitter rival, wants him dead.

The Security Service believes that another British-based Russian, named only as E1, is the middleman in the plot and would "facilitate" the murder of Zakayev. Judges revealed the explicit warning in a written judgment, which said: "Kadyrov, who had been responsible for the assassination of a number of his opponents, has a black list of individuals, some of whom he wished to have assassinated, and … the exiled Prime Minister of Chechnya, Akhmed Zakayev, a refugee living in the UK, was believed to be on this list."

MI5 said the attack on Zakayev "would be likely to be facilitated through [E1] who would be well placed to provide valuable information".

MI5 said E1 was involved in the killing of Umar Israilov, a former Kadyrov bodyguard who became a vocal opponent of the Chechen leader. He was shot dead in Vienna in 2009.

E1 "played a significant role in the assassination of Israilov in Austria on behalf of Kadyrov", the Home Office told judges.

But in spite of the unprecedented public nature of the warning over the apparent danger, E1 is in Britain and fighting a legal case to stay here.

The Appeal Court ruled 10 days ago that he was allowed to stay in Britain while he attempted to overturn a decision by the Home Secretary to exclude him.

E1 - a 45-year-old father of six who is believed to be a former soldier - is expected to fight to stay in Britain permanently. Although he is currently in a secure detention centre, he is also expected to take court action to be freed.

He first came to Britain in 2003 with his family as refugees, claiming asylum from the civil war in Chechnya. While his wife and family have become British citizens, he was refused citizenship in 2009, although he had previously been given indefinite leave to remain.

But there was a change in 2010, when E1 was out of the country. According to court papers, the Home Secretary "personally directed" his exclusion on May 11, 2010, which was the day the Coalition took over as the new government.

It is unclear whether this was one of the final decisions made by Labour's Alan Johnson as outgoing home secretary, or one of the first by his successor, Theresa May - but the decision underlines the seriousness of the case.

E1 was warned not to return to Britain and told he did not have the right to begin an appeal from inside this country.

However, he arrived at -Heathrow - where it is believed British security services were waiting for him, as they knew of his flight arrangements, and he was detained. From confinement, he began a legal challenge to stay in Britain, saying he had a right to appeal "in country" against his exclusion under immigration rules dating from 2003.

His case went first to the Special Immigration Appeals Commission - where MI5 sets out secret cases against terrorists and other people who are considered a threat to national security - which referred his case to another court, in front of Justice Mitting.

His lawyers said the Home Office should have told him he could appeal "in country". But Justice Mitting ruled that while the Home Office had made a mistake, it did not mean that E1 should be allowed to stay in Britain to fight his case, in part because he was such a threat to national security. E1 appealed - and his case was heard by three senior appeal court judges, Lords Justice Pill, Moses and Sullivan.

Such was the concern of the Home Secretary and the security services that MI5 made an "open statement" to the judges that spelt out exactly what a threat they say E1 represents.

It detailed in explicit terms not normally put in the public domain by MI5 how agents believe he was a key part of the plot against Zakayev.

Zakayev, known as Chechnya's Laurence Olivier, is a former actor who went on to command rebels in the war with Russian forces ordered into Chechnya in 1994 by the Kremlin.  Zakayev holds the position of prime minister of the "Chechen Republic of Ichkeria", the unrecognised secessionist government.

He was granted refugee status in Britain in 2003. That same year Russia demanded his extradition but it was refused by a judge, who ruled that he was at risk of torture.

MI5 believed Zakayev was wanted dead by Kadyrov - a man who has a tiger for a pet. He has been repeatedly criticised by human rights groups but is a key ally of Vladimir Putin, the Russian president.

Zakayev is a close friend of Miss Redgrave, the political activist who comes from one of Britain's most prominent acting dynasties, and has championed the Chechen cause since 1999. She put up a £50,000 surety to secure his bail during his extradition battle. He was also a friend of Alexander Litvinenko, the dissident former KGB officer who was killed with radioactive poison in London in 2006.

Despite MI5's evidence to E1's challenge against exclusion, the three appeal court judges overturned the previous ruling and said he had the right to be in Britain and have his case heard.

The Home Office will continue its fight to have him deported and can consider an appeal to the Supreme Court.

Legal experts warned that E1 could also have a "human rights" case to stay in Britain because of his family.

A Home Office spokesman said: "The court's decision does not change the fact that we intend to deport this individual from the UK.

"The Government's highest priority is to protect public safety and national security. Where a foreign national poses a threat to this country, we will seek to deport them."

The case raises concerns over Britain's ability to keep people who are threats to national security out of the country - especially if they have been previously granted permission to stay.

MI5 is known to be concerned about the number of citizens of Russia and other former Soviet Bloc countries who are in Britain. They fear that London could increasingly become the place where political and gangland scores are settled - a fear that escalated after the attempted murder last month of Gorbuntsov in Canary Wharf, east London.

Zakayev said yesterday he had not been notified of the alleged plot against him, but said he knew of previous assassination attempts. "There are more Russian spies in Britain today than there were during the Cold War," he said.

"I think the British authorities know this and the British security service knows this. Nothing will change until Vladimir Putin loses his position in Russia.

"They will continue to attempt to harm me, and all their political enemies."

The case is the latest that highlights the refusal of judges to remove threats to security, highlighted by the continued presence in Britain of Abu Qatada, described as Osama bin Laden's "right hand man in Europe".