A teenager who plotted "mass murder" at an Elton John concert on the anniversary of the 9/11 attacks was snared by an undercover MI5 officer who met him in Slough and recorded their conversation.

Haroon Syed, 19, tried to get a suicide vest and machine gun and identified the Hyde Park event as a possible target, but was snared by Security Service agents posing online as a fellow extremist.

He was jailed for life yesterday, July 3.

The Old Bailey heard how key evidence came from Syed's chat with fake contact Abu Yusuf via mobile phone and social media.

Syed asked for "gear" for his "op" and when asked to give details, he said he needed a machine gun and an explosive vest "so after some damage with machine gun do martyrdom ... that's what I'm planning to do".

Initially he cried off meeting his contact, complaining that he was being followed by police who will "have eyes on me if I come".

An officer pretended to be Abu Yusuf when they did finally get together at a Costa Coffee in Slough, and their discussion was secretly recorded.

Syed repeatedly urged the officer to get him weapons for free as he was turned down for bank loans purporting to be for a motorbike, a wedding and home improvements.

On August 30, Syed stressed that he needed a "portable" device, saying: "I might put the bomb in the train and then I'm going to jump out so the bomb explodes on the train.

"So ask the brother if he can make that type of bomb with button."

Syed arranged to pick up the bomb in exchange for £150 the following week.

He asked Abu Yusuf to make sure there were lots of nails in it and added: "I was thinking of Oxford Street.

"If I go to prison, I go to prison. If I die, I die, you understand."

Syed was indoctrinated by Al-Muhajiroun (ALM), the banned group linked to jailed preacher Anjem Choudary, before he set about planning a bombing on British soil.

The Old Bailey heard a trigger for his radicalisation was the arrest of his older brother for plotting an Islamic State-inspired Poppy Day attack.

Syed, from Hounslow, west London, admitted preparation of terrorist acts between April and September last year.

Judge Michael Topolski QC said the risk Syed posed warranted a discretionary life sentence and ordered him to serve a minimum of 16 and a half years.

He told Syed: "Overall you were, and you remained, intent upon and committed to carrying out an act of mass murder in this country.

"You were not lured, you were not enticed, you were not entrapped.

"You became ... deeply committed to the ideology of a brutal and barbaric organisation that sought to hijack and corrupt an ancient and venerable religion for its own purposes and you wanted to be part of it."

Despite the risk around the time of his brother's arrest, Syed slipped through the net of the Prevent anti-radicalisation team although his passport was seized in 2015.

Mitigating, Mark Summers QC said it was a "crude, ill-thought-out" plan made at the behest of others.

Syed now publicly rejects his past beliefs and condemned the recent bomb attack at the Ariana Grande pop concert in Manchester, the lawyer added.

Last June his brother, IS-inspired Nadir Syed, 23, also from Hounslow, was jailed for life with a minimum term of 15 years after he was found guilty of plotting to carry out a Lee Rigby-style beheading around Remembrance Sunday in 2014.

Deb Walsh, of the Crown Prosecution Service, said: "Haroon Syed is clearly a danger to the public who was prepared to carry out indiscriminate attacks against innocent people.

"The compelling evidence presented by the CPS left him with no choice but to plead guilty."

Commander Dean Haydon, of the Met's Counter Terrorism Command, said: "Our close working relationship with MI5 ensured we uncovered evidence that Syed was plotting to kill innocent members of the public.

"Today's sentence has ensured that a dangerous individual harbouring violent terrorist ambitions has been removed from our community."