A Muslim convert plotted a terror attack on Oxford Street despite repeated attempts by authorities to deradicalise him over a decade.
Former Royal Mail worker Lewis Ludlow, 27, of Rochester, Kent, said he was filled with "animosity and hatred" when he swore allegiance to Islamic State, the Old Bailey heard.
All the while, he appeared to engage with the Prevent deradicalisation programme, having 16 meetings and a phone call with officers over six months before his arrest last April.
One of the meetings was on the same day Ludlow carried out reconnaissance of targets around the capital, taking photographs of Oxford Street and Madame Tussauds.
Ludlow planned to kill up to 100 people in a "ram attack" after being stopped by police at Heathrow Airport in February 2018 as he attempted to board a flight to the Philippines.
The defendant, who called himself "The Eagle" and "The Ghost", had bought a phone under a false name and wrote down his attack plans, which were later found ripped up in a bin.
He pleaded guilty last year to plotting an attack in the UK and funding IS in the Philippines and appeared at the Old Bailey on Thursday to be sentenced.
Prosecutor Mark Heywood QC set out Ludlow's past association with extremists in Britain and abroad.
He said the Prevent programme had attempted to engage with Ludlow since November 2008, when his college had raised concern about his religious beliefs and carrying a knife.
In 2010, Ludlow attended a demonstration led by radical preacher Anjem Choudary and his banned Al-Muhajiroun (ALM) group.
He was pictured with the convicted terrorist Trevor Brooks and had secret communication with British Jihadi Junaid Hussain, who was killed in a drone strike in Syria.
In June 2015, he discussed with Hussain doing something before travelling abroad and mentioned his job at Royal Mail.
He wrote: "At my job at a Royal Mail warehouse we had a book that mentions how staff look out for suspicious items like bombs.
"I'm thinking should I find this info out more as Royal Mail rarely check items. It is perfect to send something lethal through."
Hussain told him it was a "good idea" and Ludlow promised to "look into it".
That year he was arrested and IS material was recovered from Ludlow's phone but no further action was taken.
Ludlow had cut off contact with Prevent two years before but resumed meetings with officers in November 2017, while keeping his true feelings under wraps.
In January 2018, he bought a ticket to fly to the Philippines on February 3 but was stopped at the airport and had his passport seized.
In March, having set up a PayPal account and an Antique Collections Facebook site, he sent money to an alleged extremist called Abu Yaqeen in an area of the Philippines with a significant IS presence.
Police went on to recover torn-up scraps of paper from Ludlow's bin detailing potential attack sites in Britain.
On Oxford Street, he planned using a van and mounting the pavement, noting the lack of safety barriers.
He said: "Wolf should either use a ram attack or use ... on the truck to maximise death ... it is a busy street it is ideal for an attack. It is expected nearly 100 could be killed in the attack."
Mr Heywood said there was evidence the defendant wanted to recruit a second attacker as he did not have a driver's licence and was "scared" of crashing.
On April 13 last year, Ludlow's mobile phone was retrieved from a storm drain and found to have videos of the defendant swearing allegiance to IS and evidence of "hostile reconnaissance".
In one of the videos, the hooded defendant said: "I, the Eagle, have pledged allegiance to Dawlatul Islam and also, this is a little message to you people, there is no love between us, there is nothing between us except animosity and hatred."
In mitigation, Rebecca Trowler QC said autistic Ludlow was directed by the extremist in the Philippines and his plans were "embryonic".
Giving evidence, Ludlow, who converted to Islam at 16, told how he dropped out of school after he was bullied for nine years.
He said: "I was a loner. I was on my own and it was sad. People would say they found me too strange.
"It was really depressing. I felt everyone hated me and I thought I would be better off dead."
Describing feelings of anxiety, he said: "Physically I feel my heart beating rapidly, adrenaline rushing. Mentally, the things that come into my head are death and disturbing images to do with graves, worms, decomposition."
Ludlow said he found ALM online and was invited to demonstrations.
At first it was "friendly" and he was seen as "funny" but after two years things turned sour and he was suspected of being a spy, he said.
Ludlow told the court how MI5 tried to recruit him as a "spy" a year before he hatched his terror plot.
The defendant, who claimed benefits for eight years, had met a member of the security services near his family home in Rochester in March 2017, it was claimed.
During the meeting, an officer told him he "could be useful to us" and offered him £50, Ludlow said, adding: "I thought, 'Are they asking me to be a spy?'"
Afterwards, Ludlow said he was "harassed" over the phone, adding: "It seemed to me they wanted me to entrap people."
The sentencing hearing is due to go on for up to three days before Judge Nicholas Hilliard QC.