The leader of the English Defence League was has been jailed for 10 months after admitting using someone else's passport to travel to the United States.
Stephen Lennon, 30, pleaded guilty to possession of a false identity document with improper intention, contrary to the Identity Documents Act 2010, at Southwark Crown Court.
Lennon, who often calls himself Tommy Robinson, used a passport in the name of Andrew McMaster to board a Virgin Atlantic Flight from Heathrow to New York, but was caught out after his fingerprints were taken by customs officials.
Stephen Lennon aka Tommy Robinson addresses the EDL in Blackburn
He left the airport and entered the US illegally but left the country the following day, using his own passport to return to the UK.
EDL members have frequently held vigils outside the prison, calling him a "political prisoner".
Lennon has a chequered history of run-ins with the law. Searchlight magazine reported that he was convicted in April 2005 for assaulting an off-duty police officer who had intervened to stop a confrontation between Lennon and his partner.
In 2010 he was convicted of having used "threatening, abusive or insulting behaviour" at a EDL brawl in Luton, arrested in 2011 for breach of bail conditions while at a demo in Tower Hamlets - leading him to go on hunger strike in Bedford Prison, refusing to eat the prison's "halal meat".
The court heard that Lennon, who had previously been refused entry to the US, used his friend's passport to travel to the country in September.
But when he arrived at New York's JFK Airport, customs officials who took his fingerprints realised he was not Mr McMaster.Lennon was asked to attend a second interview but left the airport, entering the US illegally.
He stayed just one night and travelled back to the UK the following day using his own legitimate passport - which bears the name Paul Harris.
The court heard that is the name that appears on the EDL leader's passport, although he uses aliases.
Lennon, who was arrested in October, was jailed for 10 months today.
The court heard that he was previously jailed for assault in 2005 and also has previous convictions for drugs offences and public order offences.
Sentencing the 30-year-old, Judge Alistair McCreath, told him: "I am going to sentence you under the name of Stephen Lennon although I suspect that is not actually your true name, in the sense that it is not the name that appears on your passport.
"What I have to deal with you for is clear enough.
"You knew perfectly well that you were not welcome in the United States.
"You knew that because you tried before and you had not got in, and you knew the reason for that - because, rightly or wrongly, the US authorities do not welcome people in their country who have convictions of the kind that you have.
"With that full knowledge, you equipped yourself with a passport. I am told that it was given you by way of a loan from your friend Andrew McMaster, to which you bore, I am told, some resemblance.
"And by use of that passport you did what you could to get into the United States.
"But you did not get in because they took your fingerprints and they worked out that you were not who you claimed to be.
"I am told that, by whatever means, you slipped away from the US authorities, got into the country and then very rapidly - and understandably so - got out of it."
Stephen Lennon (AKA Tommy Robinson) passes between police officers during a rally in Luton
He said Lennon had used his own passport to get out of the US, adding: "You did so, I am quite sure, in order to avoid the consequences that would have fallen upon you had you been caught by the authorities in America."
The judge went on: "What you did went absolutely to the heart of the immigration controls that the United States are entitled to have.
"Had it been known in this country that you were proposing to leave under a false passport, you would not have been accepted on to the plane and you would not have been permitted to leave this country on a false passport.
"It's not in any sense trivial."
He sentenced Lennon to 10 months in prison, minus the days he has already served in custody.
Prosecutor Simon Sandford said it was the Crown's case that Lennon committed the offence while on bail for breaching an International Football Banning Order - of which the court heard he was acquitted.
In mitigation, his defence barrister, Giles Cockings, told the court that Lennon had not stolen the passport, and had only used it for a day.
He told the court his client had pleaded guilty straightaway, demonstrating "a certain amount of courage".
"Perhaps what screams volumes from this particular case are two main areas," he told the court.
"Firstly, this passport was not stolen, it was lent by a friend for whatever purpose.
"Secondly, he was only using the passport, it transpires, for a day and a half. In fact he only spent one evening in the United States of America.
"I think the intention was simply to avoid a necessity for a visa into the United States.
"Upon realising that in actual fact it was not going to assist matters, on realising he had committed an offence, he used his own passport to come back.
"It is not, I would suggest, the most aggravating of cases of this kind."