LONDON: A prominent anti-migrant activist has been arrested after an alleged boat slashing incident in the Channel earlier this week, UK media reported Thursday.

It came as the interior ministry confirmed 781 people arrived in Britain on Wednesday after crossing the busy waterway from France aboard small boats — a daily record for this year.

The annual arrival of tens of thousands of migrants on the boats has become highly contentious in the UK, seized upon by the hard right and helping to fuel growing anti-immigration sentiment.

The arrest of Daniel Thomas, a longtime ally of far-right figurehead Tommy Robinson — real name Stephen Yaxley-Lennon — comes after he spearheaded several demonstrations involving black-clad masked men, some of which turned violent.

Thomas, 37, was arrested late Wednesday on suspicion of destroying ships or endangering people’s safety and criminal damage with intent to endanger life, British media reported.

Hampshire Police in southern England confirmed the arrest of a 37-year-old man but did not name him, in line with UK policing protocols.

“A man has been arrested after a boat that had an emergency responder on board, was damaged in the English Channel,” the force said in a statement, adding he remained in custody.

Thomas, better known by his nickname Danny Tommo, livestreamed Tuesday from a boat in the Channel, on a self-proclaimed mission to track small boats bound for Britain.

Footage later emerged online appearing to show him slashing an inflatable craft, apparently with a French rescuer still on board.

“This is English territory. It’s not France anymore,” Thomas shouts in the video, before repeatedly yelling “get off the boat” at someone dressed in the orange uniforms worn by staff from France’s SNSM lifeboat service.

Yaxley-Lennon emailed supporters on Thursday appealing for donations to help his former right-hand man.

Meanwhile, interior minister Shabana Mahmood has ordered an urgent review after two small boats avoided border forces and landed on southeastern English beaches this week.

Successive UK governments have grappled with how to curb the crossings.

Wednesday’s 781 new arrivals meant 18,565 people had arrived via the route so far this year, down 42 percent year-on-year.

The center-left Labour government has said the reduced numbers vindicate its strategy of targeting the criminal gangs facilitating the perilous journeys and working in closer collaboration with European neighbors.