The former altar boy built the device at home with a £2 clock from Tesco after googling an al Qaeda article entitled Make A Bomb In The Kitchen Of Your Mom.
The Greenwich Peninsula Jubilee line station was evacuated on October 20 previous year at 11am just two minuted before the home made bomb was due to go off.
"I would like to praise the public who informed the train driver of the abandoned bag; due to their quick intervention we were able to make it safe and identify Smith".
Damon Joseph Smith, aged 20 from Rotherhithe, London, was found guilty earlier this week of unlawfully and maliciously making or having in his possession or under his control an explosive substance with intent to endanger life or cause serious injury to property.
And today, the autistic defendant smiled in the dock as Judge Richard Marks sentenced him to 15 years in a young offenders' institution.
Judge Marks said Smith's actions took place in a "background of fear" of terrorism, an "all too timely reminder of which were the events in Manchester", the London Evening Standard reported.
Smith's lawyer, Richard Carey-Hughes QC, said Smith was "sorry" for the fear and disturbance he had caused and had "learned his lesson".
He was caught on CCTV carrying a holdall shortly after 10.30am earlier that morning as he entered Surrey Quays Station where he caught an Overground train to Canada Water before switching to a westbound Jubilee Line train. Both the train and North Greenwich station were evacuated.
It was only when he noticed a wire poking out of a clock that he raised the alarm.
A handwritten shopping list of items used to make the tube bomb was also found torn up.
Smith told the arresting counter-terrorism officers that he had made the bomb, but that it was only meant to spew harmless smoke as a Halloween joke.
Smith told officers he was interested in Islam, but was not an extremist.
The court heard that experts were divided over Smith's future risk to society.
I am influenced by your history of preoccupation with weapons and bombs as well as by your condition which makes it hard for you to empathise with others and to understand and fully appreciate the very serious potential consequences of your actions, as this incident amply demonstrates.