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.
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The world's first ever 'hole in the wall' was installed in Enfield, north London, on June 27 1967.
America says it has "identified preparations" for an attack similar to that which killed at least 86, including 30 children, in April.