Amid chaotic scenes, French gendarmes waded into shallow waters off a beach south of Boulogne and used knives to slash an inflatable small boat, packed with men, women and children, that was wallowing, dangerously, in the waves.

The intervention was highly unusual. French police usually follow strict rules that bar them from going into the sea in case they put lives at risk.

It is possible to see this rare incident as evidence that the French police, under growing pressure to stop a surge of small boat migrant crossings to the UK, are changing their tactics.

The “taxi-boat”, with almost no passengers, came towards the shore, watched by a French coastguard boat further into the Channel. Initially, people were ushered forwards in organised groups, holding hands, and directed by one man who appeared to be leading events. But as the inflatable boat turned and reversed towards the shore, there was a scrum as dozens of people scrambled to climb aboard in water that was at least waist deep.

At first the gendarmes declined to intervene and stood watching from the shore. One officer repeated a now-familiar explanation to BBC correspondent Andrew Harding – that they were barred from going into the water except to rescue people. But as the situation became increasingly chaotic, the officers at the scene clearly felt that a line had been crossed, that those on board were now in danger, and that there was a brief opportunity to disable the boat in relative safety.

Moments later the boat was dragged ashore by the police as the migrants began collecting items they’d dropped on the beach and then headed inland, up the sandy paths through the dunes towards the nearest village and a bus-ride back to the migrant camps further north.