It’s the end of summer and the long beach of Calais is dotted with British tourists enjoying the last few days of their holiday. Kids build sandcastles and run around hunting for hidden treasures. A few brave swimmers splash in the shallows. Along the promenade couples swing their legs over the sand and throw chips to the gulls. On a clear day like today you can easily see all the way across the Channel to the white cliffs of Dover, gleaming in the sunlight.