A man who attacked Guardian columnist Owen Jones outside a London pub late at night in August had a collection of far-right memorabilia, and a photograph of himself making a Nazi salute, a court heard on Thursday.

Prosecutors said that the “insignia and memorabilia” found at the home of James Healy, from Portsmouth, was relevant in determining whether the late night assault on the leftwing journalist was motivated by far-right or homophobic sentiment in a trial at Snaresbrook crown court.

Healy, 40, is one of three men who have already pleaded guilty to assaulting Jones in an incident that took place at around 2am on 17 August last year outside the Lexington public house in King’s Cross. But if a judge decides that the incident was motivated by aggravating factors, Healy faces a higher sentence.

The evidence produced in court included a printout of a photograph of a younger Healy making an Nazi salute. His defence counsel said it was taken “when he was a teenager, 20 years ago”, but the prosecution said that it was printed out in 2015 and found in his house.

The collection of memorabilia and badges found after a search in late August featured symbols from far-right group Combat 18, banned terror group the Loyalist Volunteer Force, and Chelsea Football Club.

Philip McGhee, prosecuting, said that on one of the badges was written “Combat 18 and white power”, with a St George’s flag in the centre, overlaid with a snarling bull dog. Another badge featured a “sun cross” – a white supremacist symbol – used by White Pride Worldwide with the “whatever it takes” motto of Combat 18 and “lead the way” used by the Loyalist Volunteer Force.

“The person who possesses these items has sympathy for white supremacists, far-right, and homophobic organisations,” McGhee said, adding that they would therefore “bear antipathy for those on the left wing of the political spectrum and those with a non-heterosexual sexual orientation”.

But Matthew Radstone, for the defence, said that the insignia and memorabilia had no relevance to the attack and should not be considered as evidence by the judge. Radstone said his client had previous football-related convictions, that he was part of a “risk group” of Chelsea supporters and that possession of the items was “consistent with Mr Healy being a Chelsea football supporter”.

Anne Studd QC, the presiding judge, concluded that “it would be wrong to exclude this evidence” but added that including it did not mean it would form an important part in her final ruling on the case, which continues into Friday.

Earlier McGhee, setting out the case, said: “It is said, based on the evidence, that the assault was motivated by hostility borne by the defendant towards the victim either due to the victim’s sexual orientation or political views, or both.

“The defendant asserts that the only motivation was something that happened between him and the victim inside the public house outside which the assault took place.”

Studd, presiding, said it would be for her to adjudicate. “My job is to look at motivation,” she told the court, adding that she would examine CCTV, what was said and done at the time, “whether there is any relevance in the memorabilia found at his home address” and whether Jones was known to the defendant.

Jones, 35, said he had been out celebrating his birthday and was attacked outside the pub at about 2am on 17 August while he was saying goodbye to friends.

Healy is one of three men who have admitted being involved in the incident. He and Liam Tracey, 34, from Camden, London, and Charlie Ambrose, 29, from Brighton, all pleaded guilty to affray last month. Healy also admitted a further charge of assault occasioning actual bodily harm.

Jones is expected to give evidence on Friday. Sentencing for all three is due to take place in February at the earliest.

The prosecution also said that a black flag had been found at Healy’s home, bearing a “totenkopf” skull and cross symbol, which it said was a symbol used by the Chelsea Headhunters, the principal hooligan group associated with the west London Premier League club. “The image of the skull was also used by the Nazis,” McGhee said.

Also on the flag were the letters CYF, said by the prosecution to stand for Chelsea Youth Firm, another hooligan group associated with the club. The hooligan groups were described by McGhee as “fertile ground for rightwing groups, the National Front and the BNP [British National Party]”.

Another badge found at Healy’s home said “Chelsea FC no asylum seekers” while another said “England – no surrender” repeating a familiar slogan used by loyalist groups in Northern Ireland.

Healy’s counsel, Radstone, said there was an alternative explanation for what had happened on the night. He said that Jones had barged into Healy in the Lexington pub previously and that he had spilt his drink and not apologised. Studd said she had seen CCTV footage of that incident and of the late-night assault, which she would also take into account in her final ruling.

Radstone, for Healy, said there was nothing in the incident itself that revealed any discriminatory motive, although he accepted he was angry and probably swore during the attack.