There maybe a triple ring of security protecting the United Kingdom, but there's a great big hole in it called Calais. As long as the French allow thousands of what are, illegal aliens on French soil, to just wander around unhindered in France on the grounds that, it's OK, they don't want to stay in France so they're not our problem because they're on the way to the UK, then we will continue to have thousands coming into the UK every year in the back of trucks, never to be returned to they're countries of origin because they have no passports or ID of any kind.
Iain