Aid organisations said migrants camped in Calais had made last-ditch attempts to cross the Channel ahead of today's operation.
Border police were said to have spotted groups of up to 40 people hiding in bushes along roads leading to the port.
Some were attempting to jump on lorries as they slowed down.
More top news
Rain across central Britain with longer, intense downpours with thunder in places this evening. A lucky few will stay sunny and dry.
Planning on going to the London Marathon tomorrow? Read our handy guide first!
Labour plans to cap above-inflation rent rises over a three-year period, if they win the General Election.