The Migrant flotilla escalation coming across the La Manche and then the English Channel [was] should have been easily predictable,
just after Angela Merkal waved her arms to the words "We can do it" back in August 2015, as Bashar Al-Assad was bombing his cities and displacing his excluded, alienated, disenfranchised and neglected citizens.
Angela Merkal's words were heard far and wide and have added to the already
problematic flow of economic migrants steadily heading north and west towards Europe. Most seeking something more than their corrupt, neglectful & or & warring governments fighting over control of western currency and western deals over currency possession.
But that is another problem and needs a much more complex solution.
The problem for Britain is that the government did not [through intention or neglect] create a plan for protecting the British shore-line border.
Since 2008 [The 'UK's Unconstitutional' signing of the Lisbon Treaty in 12/2007] Britain took the last physical and mental step to open [idealist] borders and [Re-Roman-esque, Euro-responsibility-identity.
[It should be important to note that Roman citizenship was preciously valued,
strongly guarded and highly coveted]
It was the initial flow of E.U migrants that when added to the newer E.U member states
that has led to local British discomfort growing into the anger and home alienation that led to the non-constitutional-thinking-political voter to vote to leave the E.U.
[Although that voting force has yet to be addressed by any political leader apart from Nigel Farage.]