A teenage London Muslim convert who idolised the killers of Lee Rigby faces prison today for planning a copycat public beheading of a British soldier.

Brusthom Ziamani was 18 when he was arrested with a hammer, knife and black Islamic flag walking through Whitechapel.

He admitted later that he wanted to decapitate a soldier and hold up his severed head for a friend to take a photograph.

He even spoke of attacking Prime Minister David Cameron if he ever got the chance.

Ziamani described Michael Adebolajo, one of the Islamic extremists who killed Lee Rigby on the streets of Woolwich, as "a legend."

To emulate his hero he researched the locations of military bases and army cadet centres in south-east London.

Yet Ziamani had been born into a strict Jehovah Witness family originally from the Congo before converting and attended meetings and demos organised by the banned terrorist group Al-Muhajiroun (ALM).

He changed his name to Mujahid Karim and looked up to extremist preachers such as Anjem Choudhary, the co-founder with Omar Bakri Muhammed and Abu Hamza.

Ziamani, now 19 of Camberwell, was convicted at the Old Bailey of preparing for acts of terrorism.

He will be sentenced on March 20 by Judge Timothy Pontius, when, the court heard, he would receive a term of “very considerable length.”.

During the two week trial the court heard how he had shown his then girlfriend a hammer and 12-inch knife and boasted of a terrorist attack to "kill soldiers."

In a series of Facebook messages and letters he revealed how he hated non-believers and dreamed of martyrdom.

He wrote of going to paradise and said he had a “duty” to help people being raped, tortured and killed in Iraq and Syria.

In one letter found by police at his flat he wrote: "You want war, you got it. British soldiers' head will be removed and burned. U cannot defeat Muslims. We love to die the way you live."

Ziamani had started dating his ex-girlfriend he had met over Facebook in March last year.

But when she returned from holiday in Ireland a month later she found he had started wearing Islamic clothing and wanted her to follow him and convert.

When she refused he and ended their relationship he sent her messages on the mobile phone app Whatsapp threatening to “wipe her out."

In June he had made internet searches for Camberwell army cadets and the London Irish Rifles Association.

In June last year police raided his Camberwell home and found five sheets of letters he had written – much of it gloating over the Lee Rigby murder.

In the first he wrote that: "I will wage war against the British Government on this soil. [It] will have a taste ov there own medicine. They will be humiliated. This is ISIB Islamic States of Ireland and Britain."

He also wrote: "you people will never be safe" adding "we will send you all to hell fire, you want war, let's kill them, slaughter hem and implement sharia in our lands and UK. Kill every gay, every shia, every les."

On another sheet he wrote: "Lee Rigby is burnin in hell. Woow I'm dying, good for him, this is what you get for voting Cameron and democracy, my brothers who are Lee Rigby's killers are in prison getting food clothes and shelter and its being paid for by Lee Rigby's family HAHA."

"Brothers pick up your swords gins boms take off there lims, we should do a 9/11 and 7/7 and Woolwich all in one day, every day for eight years."