Public concerns about immigration were at the heart of the vote to leave the EU. Since then, the government has been silent on their plans. But with just a year to go until the country leaves, there are big unanswered questions about how any new system will work after Brexit - and the issue still stirs up powerful emotions. Nick Robinson travels from the heartlands of the leave vote to the front line of the NHS to find out what immigration the public wants and what Britain's businesses and public services say they need, and to ask the big question: who should we let in?