Filip Golon Bednarczyk, 26, denied planning an attack or attempting to make a bomb and claimed he was acting on “curiosity borne out of boredom”.
Giving evidence at the Old Bailey on Tuesday, he said he had downloaded numerous terrorist manuals and collected chemicals and components because he wanted to make fireworks.
But a judge said Bednarczyk’s explanations did not “bear scrutiny” and that he was interested in building bombs.
“I find your admitted right-wing sympathies were the motivation for your interest in explosives,” Judge Anthony Leonard QC told him.
“The idea you drew a circular diagram with nails and a detonator because you wanted to create a firework is fanciful … if the instructions had been followed it would have resulted in a working IED.”
He also pleaded guilty to seven charges of possessing a document likely to be useful to a person committing or preparing an act of terrorism in relation to various titles about homemade explosives and devices.
The judge sentenced him to four years in prison with another year on licence, and handed Bednarczyk a 15-year notification order in which he has to report his personal details to the police.
When entering his guilty pleas, Bednarczyk insisted he did not want to harm anyone and had not attempted to construct a bomb.
He admitted “right-wing sympathies” but denied being a neo-Nazi and said his online research had not focused on particular groups.
An analysis of his electronic devices revealed an interest in firearms, knives and killings as well as extreme right-wing views.
Filip Golon Bednarczyk cutting up a Britain First membership card in a 2017 YouTube video
The Old Bailey heard that he had a copy of the Christchurch attacker’s manifesto, which claimed white people are being “replaced”, and shared memes supporting the terror attack that left 51 people dead.
Bednarczyk had also searched the internet for Nazis, Hitler, the Polish Defence League — an offshoot of the English Defence League — and Britain First.
The Polish national, from Luton, had targeted Muslims, Jews and the gay community in hateful online posts.
In a Facebook post from July 2019, he shared photos of British police officers supporting Pride events and called them “pathetic”, writing: “Death of European culture and values”.
In 2015, Bednarczyk “liked” a meme showing Mecca being destroyed by nuclear weapons, and called for the burqa to be banned.
Another post suggested that “liberal blood will flow in the streets” for the tolerance of Muslims, transgender people, homosexuality, abortion and feminism.
The previous year, he shared an antisemitic meme which originated on 4chan showing world leaders wearing Jewish skullcaps.
On his YouTube channel, which has more than 4,000 subscribers, Bednarczyk uploaded a video of himself cutting up a Britain First membership card in 2017.
He was arrested by detectives from the Metropolitan Police's counter-terrorism unit on 11 December.
A search of his bedsit led to the discovery of handwritten notes, electrical component parts and a 2kg bag of sulphur powder inside a wardrobe.
Printed bomb-making instructions were found alongside a blank-firing pistol, a soldering iron and USB stick containing documents and images relating to explosives.
Expert analysis of the material was that it included “viable instructions for a range of explosive materials including low explosives, primary high explosives and secondary high explosives” and “viable instructions for a number of types of IED”, prosecutor Dan Pawson-Pounds told the court.
Bednarczyk said he bought potassium nitrate and sulphur over the internet but later tried to return them because he “lost interest” in it.
He said he did not open the sulphur and told the court: “Out of boredom I was thinking about experimenting with the chemicals for a little excitement in the garden.”
The defendant claimed he had forgotten about the items in his wardrobe and had accidentally downloaded terrorist manuals because he was taking documents off the internet “in bulk”.
Judge Leonard said it was not a “coincidence” that Bednarczyk had kept electronic parts that could have been used to make a detonator alongside the ingredients for gunpowder.
The judge said he was previously warned against keeping such material in March 2018, when police confiscated chemicals discovered at Bednarczyk’s home after his partner’s suicide.
Around that time, the defendant confided in a friend that he was concerned about what police would discover if they searched his computer, because he had been looking at how to make a bomb.
The court heard that Bednarczyk, who has a seven-year-old son in Poland, may have exaggerated symptoms of poor mental health during a psychiatric assessment and did not suffer from a condition that affected his culpability.
Defence barrister Beth O'Reilly told the court there was “no evidence of a terrorist connection” in the case, adding: “He describes his interest [in explosives] as curiosity, that interest wasn’t acted on.”