Among the new Britons taking part in citizenship ceremonies today will be one man who has already put his life on the line to protect his adopted country.

Reda Hassaine will stand in Islington Town Hall, North London, to affirm allegiance to the Queen and pledge to give his “loyalty to the United Kingdom and to respect its rights and freedoms”.

Mr Hassaine’s journey to this point has been long and dangerous. An Algerian who went undercover in Finsbury Park mosque to gather information on extremists, he has endured beatings and death threats, and abandonment by his spymasters. After years of fighting to be British, he told The Times: “At last I can look forward to planning my life, to being able to travel freely. I will be so proud to call myself a British citizen.”

Mr Hassaine, 46, arrived in Britain in 1994, one of thousands fleeing the civil conflict between Islamist guerrillas and the Algerian military. As a journalist, he was under threat of death from the Islamists, and, after a friend was murdered, he volunteered for the Algerian secret services. He began attending mosques in North London where exiled members of the Armed Islamic Group were raising funds and planning attacks in Algeria and France.

Mr Hassaine was also asked to pass information to DGSE, the French intelligence service, and he established contact with the London embassy. Their interest in his work grew as Abu Hamza al-Masri turned the Finsbury Park mosque into an extremist haven. Mr Hassaine alleges that the French discussed kidnapping the cleric.

By the end of 1998 Mr Hassaine was working for Scotland Yard’s Special Branch before being passed to an MI5 handler. He continued to report on the activities of Abu Hamza and Abu Qatada, the Palestinian cleric who ran a Friday prayer group from a community centre near Baker Street. But Britain did not regard the growing band of Islamistswith the same seriousness as either France or Algeria. The French nicknamed the city Londonistan but at the end of the 1990s the main terrorist threat to Britain was still assessed to be the IRA and dissident Irish republican groups.

In 2000 Mr Hassaine’s cover was blown and he was badly beaten by Abu Qatada’s henchmen. He claims that his MI5 handlers, who he says had promised him British citizenship in return for his information, dropped him.

“I volunteered to work for the intelligence services of all three countries because all of them had the same enemy,” he said. “The only reward I expected was from God, who teaches that if you save a life it is like you have saved all of humanity and if you kill it is as if you have killed all of humanity.”

After September 11, 2001, Mr Hassaine became a prominent whistleblower, revealing how Britain had turned “a blind eye” to the Islamist threat.

His decision to go public seemed to threaten his hopes of citizenship. His former wife and his two children became citizens in 2005 but he had to wait. In a letter to Treasury solicitors, Mr Hassaine’s lawyers wrote: “Mr Hassaine was paid very little for his work but agreed to do so on the promise that citizenship would be arranged for him and his family and that he would be protected. Instead he has been threatened with deportation and his life has been put at great risk.”

This month the Home Office wrote to Mr Hassaine congratulating him. He said: “This is all I ever wanted. It gives my life a security that it has lacked for years.”

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