The show is about DCI Sam Tyler who is somehow transported from super-contemporary Manchester back to 1973 and the old-school policing of Gene Hunt and his unit. All he has to do is bide his time until he works out how to get home...
The best thing I've seen in years: excellent concept, excellent execution and wonderful heart. The level of detail is also remarkable and it has a fantastic sense of style.
While it is near inconceivable for me to admit anyone couldn't like this show, I guess I should warn you that it is extremely British in places and some of the references could be a little obscure to an international audience.
To conclude: very British but that's what makes it great.