Far-Right activist Tommy Robinson was detained and interviewed by police under counter-terrorism laws after returning to the UK from Russia.
The 43-year-old announced on social media he was held at Heathrow Airport on Saturday ‘for the best part of three hours’.
Robinson, who has previous convictions for violent crime, public order offences and fraud, wrote: ‘I’m a terrorist again.’
He had been in Moscow, where he met with Errol Musk, the father of billionaire Tesla founder Elon Musk.
The former English Defence League founder, whose real name is Stephen Yaxley-Lennon, also attended the annual Kremlin-backed economic forum, described as Russia’s answer to Davos.
In a statement, the Met said: ‘Officers stopped a man in his 40s at Heathrow Airport at around 5pm on Saturday, 13 June, following his return to the UK from Russia via Turkey.
‘He was stopped under the provisions of Schedule 3 of the Counter Terrorism and Border Security Act 2019.
‘The man was interviewed by officers and his communication devices were seized.
Tommy Robinson, whose real name is Stephen Yaxley-Lennon, was held by police at Heathrow airport under counter-terror laws
‘He was subsequently released.’
Robinson suggested he was going to take legal action following his temporary detention.
He wrote on social media: ‘I have been detained at Heathrow Airport today for the best part of three hours.
‘I was detained under section 3 of the Counter-Terrorism and Border Security Act 2019.
‘My phone has been seized by the police.
‘So here we go again, looks like more defence and court fees ffs!!!
‘Absolute f***ing madness.’
He suggested he was grilled because the Government want ‘to see who (Robinson) is talking to’.
Robinson previously appeared at a demonstration in Southampton over the case of murdered student Henry Nowak
Robinson posted a video of himself meeting Elon Musk’s father Errol in Russia
Tech entrepreneur Mr Musk wrote on X, the social media platform he owns, that Robinson was detained because he ‘used words that the pro-stabbing politicians didn’t like’.
Robinson arrived in the UK ahead of his scheduled appearance at the Oxford Union for a discussion on Islam.
The student debate society has advertised a debate on social media titled The West Is Right To Be Suspicious Of Islam to take place on Wednesday.
Speakers also include fellow hard-right voice Laurence Fox and former Tory MP Sir Jacob Rees-Mogg.
Earlier this month, Robinson appeared at a demonstration in Southampton following the sentencing of a Sikh man for murdering university student Henry Nowak.
Vickrum Digwa, 23, was sentenced on June 1 to a minimum of 21 years in prison for the fatal stabbing of Mr Nowak last year.
The 18-year-old student was placed in handcuffs as he lay dying on the ground after being stabbed by Digwa with a ceremonial religious sword.
The demonstration materialised despite Mr Nowak’s father, Mark, making an emotional plea outside court for his son’s murder not to be used to ‘create further hatred, division or tension’.
Robinson took to social media earlier in the day of the protest, in which he described Mr Nowak’s death as ‘horrific’ while calling on supporters to attend a protest outside Southampton police station that evening.
Dozens of people were subsequently arrested and charged after disorder broke out.
The protest began outside Southampton Police Station before moving towards Digwa’s family home, where bins were set on fire and residents’ cars were vandalised.
