Iraqi asylum seeker Ahmed Hassan, 18, plotted to cause carnage in central London while pretending to engage with the anti-terrorism Prevent scheme.
He made his device with 400g of volatile “Mother of Satan” explosives packed in a bucket with 2.2kg of screwdrivers, knives, nuts and bolts.
The Old Bailey heard he wanted to cause “maximum” carnage to avenge the death of his father, who was blown up in Iraq more than 10 years before.
Hassan denied it, saying he only wanted to make a fire to fulfil a “fugitive fantasy” to be chased by Interpol which was inspired by action films.
But judge Mr Justice Haddon-Cave told him: “Ahmed Hassan, you have been found guilty by this jury at the Old Bailey of attempted murder on overwhelming evidence.
“I am now going to discuss with counsel the arrangements and timings for sentencing you.”
Hassan sat with head bowed and gave no reaction to his conviction.
Commander Dean Haydon, head of Scotland Yard’s Counter Terrorism Command, said Hassan kept his plans a secret from Prevent workers in Surrey.
The officer said: “I describe Hassan as an intelligent and articulate individual that is devious and cunning in equal measures.
“On the one hand he was appearing to engage with the (Prevent) programme but he kept secret what he was planning and plotting. We describe him as a lone actor.”
On the bomb’s potential, he said: “It was only through good fortune that it only partially exploded. If it had, without a doubt we would have been dealing with many fatalities.”
The senior officer said a review into Surrey Prevent was underway with a view to implementing “any necessary recommendations”.
The court had heard Hassan told Home Office officials he was trained by Islamic State “to kill” after he arrived in Britain in the back of a lorry in 2015.
He was taken in by foster parents Penny and Ron Jones MBE, and studied media and photography at Brooklands College in Weybridge.
But the “shy and polite” young man harboured anger at Britain for bombing Iraq even as he pursued his ambition to be the new Sir David Attenborough.
His college mentor referred him to anti-terror programme Prevent after he said it was his “duty to hate Britain” on receiving a WhatsApp message about an IS donation.
Katie Cable’s concerns were raised again just two months before the bombing when he texted her: “But your country continues to bomb my people.”
And in early September he told her: “It’s almost better to be back in Iraq. It’s better to die because you have heaven.”
While his elderly foster parents were on holiday in Blackpool, Hassan assembled the ingredients for homemade explosives in his bedroom in Sunbury, Surrey.
He used his student of the year award of a £20 Amazon voucher to buy one of the key chemicals online.
Hassan claimed he tested a sample on the kitchen table to check it would not explode, although no scorch marks were found.
On the morning of September 15 last year, he left his home and caught a train to Wimbledon carrying his bomb inside a Lidl bag.
He was captured on CCTV going into the station toilets, where he set the bomb to blow in 15 minutes, before boarding the District line.
He got off the train one stop before the bomb partially exploded on the floor of the carriage at Parsons Green.
Moments before, 93 commuters were reading newspapers and sipping cups of coffee.
They ducked for cover and scrambled to escape when a ball of fire rolled down the carriage.
Twenty-three passengers suffered burns, with some describing their hair catching fire and their clothes melting in the blast.
And 28 more suffered cracked ribs and other crush injuries in the stampede to get out of the platform via a narrow stairway.
Ann Stuart told jurors: “What I saw was this flash and whoosh that came up from my side.
“My hair was smoking. I patted myself out and got off the train and this man picked me up and held me.
“I just said to him, ‘Get me off this platform’. He shouted to everybody to get out of the way and they just parted. I heard someone say, ‘Oh my God’.
Meanwhile, Hassan destroyed his phone and changed into a Chelsea shirt as he fled London with more than £2,000 in cash but was picked up by police at the Port of Dover the next day.
Giving evidence, he claimed he only wanted to cause a fire because he was “bored and stressed”.
He said: “It became kind of a fantasy in my head. I was thinking about it. Yes, that was it.
“I was watching documentaries as well, about fugitives and just the idea of being a fugitive got into my head.”
Hassan told jurors he lied about having contact with IS to get asylum in Britain and have the chance of a “better life”.
He regretted the harm he caused “because I myself have mental scars and I know how hard it is”.
But he denied acting out of anger and guilt at being given a “safe haven” by the very country he held responsible for his father’s death.