Far-right activist Daniel Thomas has pleaded not guilty to criminal damage after a video appeared to show him slashing a boat in the English Channel.
Known to his supporters as Danny Tommo, he appeared at Basingstoke Magistrates' Court in Hampshire via videolink on Friday.
Thomas, 37, was also charged with failing to disclose the PIN to his phone, under Section 53 of the Regulation of Investigatory Powers Act 2000.
He pleaded not guilty to both charges, and has been remanded in custody.
His next court appearance will be at Portsmouth Crown Court on September 29, after Mr Thomas elected to be tried at crown court.
The court heard a crew member was on the boat while it was heard leaking air.
Prosecutor Kevin Lucie, outlining the facts of the criminal damage charge, told the court that Mr Thomas was accused of slashed an adrift boat with a knife and said: "You are on English territory. This is England. This is not France any more."
Mr Thomas was supported in the public gallery by fellow anti-migrant activist Stephen Yaxley-Lennon, also known as Tommy Robinson.
Many of his supporters also gathered outside the court.
After the hearing, Mr Yaxley-Lennon wrote on social media: "Danny is being remanded to prison. Bail refused. Outrageous.
"His legal team will now prepare to fight at the crown court for his bail."
It comes after hundreds of people gathered outside a police investigation centre in Basingstoke on Thursday evening, believing that Mr Thomas was inside.
The demonstration began shortly before 6.30pm, with protesters outside the building chanting "free DT".
