A few online searches and supermarket trips were all it took for the Parsons Green bomber to put together a potentially deadly explosive.
Ahmed Hassan had watched Youtube videos demonstrating how to make a small amount of the chemical compound TATP, having researched on Wikipedia.
Some of the footage, which he said was of people making it “just for fun” was filmed in front of children, he added.
The teenager ordered some of the key chemical ingredients on Amazon and told how he packed the device with shrapnel, bought at Asda and Aldi, to make his bomb “look serious”.
The court heard the 18-year-old used a standard kitchen timer and modified it to remove the buzzer.
A replica of the bomb – made of a silver Lidl frozen goods bag containing a white bucket, a Tupperware container wrapped in foil and a glass vase – was shown to jurors during the trial.
Hassan said he tested 50g of TATP in a Coca Cola can on the kitchen table the day before the incident, to ensure it would burn but not explode, but jurors heard there had been no marks left behind.
Just one gram of TATP can cause “serious injury to people or property”, an explosives expert said.
Sarah Wilson described the compound as a “sensitive primary high explosive” and said the 400g used in the device on the Tube train in September last year had the potential to be lethal.
Prosecutor Alison Morgan told jurors it was just “a matter of luck” that the bomb did not fully detonate and people were not killed.
Authorities are continuing to work with internet companies around regulation on identifying and reporting suspicious online purchases, police said.
Commander Dean Haydon, head of the Met’s counter terrorism command, said: “Police, various security services, agencies and the government are constantly engaging with various internet companies and looking at how such companies can get better at reporting, but also how we can put regulation – the question do we need more regulation around the purchase of precursor chemicals?
“So a bit like SAR, the banking system Suspicious Activity Reporting, looking at something similar with internet companies and how they self-report.
“There are various measures in place around reporting but also the work we do with those companies trying to flag and identify suspicious purchases.”
Ms Wilson said all the necessary elements for a viable explosive device were in the bucket and suggested it may have failed to fully explode because it had not been put together properly.
Hassan remained adamant throughout his day in the witness box that he had not meant for it to explode or cause harm, and expressed sorrow and regret for what had happened.