A Margate dad, who claimed he hurled a brick during a riot in self-defence, was betrayed by messages on his own mobile phone.
Masked Daniel Johnson, 33, said he was at the Dover demonstrations in January when he was struck by a missile.
He told police that video footage taken during the riots showed him trying to defend himself from left wing thugs and he denied a charge of violent disorder.
But a judge at Canterbury Crown Court heard how officers later downloaded messages from his mobile phone.
And it was revealed how the groundworker, from Hastings Avenue, had texted a pal three days after the riot, saying: “That was the best one yet. Already counting down the days to the next one.
“It was nice to see them on the floor getting a beating!”
Johnson later changed his plea to guilty and has now been jailed for eight months.
Prosecutor Paul Valder told how right-wing demonstrators had met outside the Dover Priory railway station intending to march through the town.
It was then that their route was blocked by left wing rivals and the police stood between the groups.
Johnson was seen holding a piece of wood and making obscene gestures towards the opposing group.
“He is then seen clearly to pick up a half brick or piece of masonry which he then hurls towards the left-wing protesters.
“Throughout the action his face is masked. He was unmasked at the beginning of the demonstration and at the end when he is seen smoking a cigarette
Johnson was arrested in May this year as he gathered for a similar demonstration and was recognised as one of the men wanted by Kent Police.
Mr Valder said: “He was interviewed and in effect said: ‘Yes, I was there. Yes, that’s me on the CCTV. I was acting in self-defence. A missile struck me, hitting me on the leg, etc, etc’.”
But after the text message was revealed, Johnson decided to change his plea and his lawyer Nicholas Jones presented personal references to the court
He said: “They show a gentler person outside what is clearly a poisonous peer group.”
Judge James O’Mahony told him: “This was not about politics and everyone has a right to demonstrate but peacefully.
“But this was just horrible, stark violence and nasty, serious public disorder. It is clear that there were those on both sides who went to Dover intent on causing trouble.
“What I don’t understand is the sheer hate on people’s faces. What’s all that about? You can have your political views but you don’t have to express them with sheer nasty visceral hate!”
After the hearing, Detective Inspector Bill Thornton said: “Dover is now considered a no-go area for such demonstrations, as we have made it very clear that the behaviour of men like Daniel Johnson will simply not be tolerated.
“He was of previous good character but has been sentenced to eight months’ imprisonment for his crimes, which shows how seriously the courts take such incidents.
“Johnson is the latest of many who have been forced to face the consequences of their violent actions on that day in Dover, and I am looking forward to hearing of further positive outcomes in the future.”