There is no trickier problem facing the Home Secretary, Theresa May, than Calais. The French port nearest to England has seen daily and nightly battles between would-be illegal immigrants laying siege to the entrance to the Channel Tunnel and the French authorities, including riot police, trying to protect it. There are said to be between 3,000 and 5,000 people living in the improvised campsites in and around Calais.Their sole aim is to smuggle themselves into England, avoiding security and immigration checks, on board heavy goods vehicles queuing up to enter the tunnel. The problems they present, including appalling living conditions in the camps and the great danger they face in trying to climb on board the trucks they target, have been there for a number of years. But this summer is th