The British courts decided some time ago that if Hollywood studios wanted to sue individuals over the alleged piracy of their movies, they would be allowed to. As such, one US company called TCYK LLC has applied for a court order that requires Sky to hand over information on certain subscribers to its broadband service.
You might be interested to learn that TCYK is a production company that produced a 2013 movie called "The Company You Keep" starring Shia LaBeouf as a journalist and Robert Redford as Robert Redford, Robert Redford also directed. The movie made about $20 million worldwide, and probably cost a lot more than that to make, so you can see why the production company wants its pound of flesh.
This is similar to other cases, including that of British porn star Ben Dover, whose company Golden Eye Limited became enraged that his adult material was being downloaded online for free. The solution for these companies is to obtain the subscriber details linked to the IP address used in the alleged infringement.
Here's where it starts to get tricky though. It's TCYK that has determined that these IP addresses are involved in downloading its material. How it does that isn't clear, nor is it made clear how certain the company must be that the IP address actually infringed its rights.
The firms operate by scaring people into paying money. That sum could be in the thousands, even though the loss related to you downloading the film is far lower.
Talk to Citizens Advice or a lawyer
What is, however, crystal clear is that once Sky is forced to give up your details, the company in question is free to send you a letter demanding money. If you refuse, or ignore the letter, it would then be able to take you to court and potentially sue you.
This is, of course, a civil matter, not a legal one, so you won't end up in jail. The court may, however, determine you did cause TCYK a loss in revenue, and order you to pay compensation.
While Sky can't help you directly, it did suggest to TechRadar that if you get a letter, you should read it carefully. If you're worried, contact your local citizens advice. We'd add that if you're really worried, it may be worth seeking the advice of a solicitor, especially if you think you have been targeted in error.
In summary then: movie studio makes expensive movie which is critically panned. Movie makes no money. People download movie without reading reviews. People then watch and proceed to hate movie. Movie studio sues people for watching a movie they hated to recover some of the money they wasted on Shia LaBeouf and his single facial expression. Profit. Maybe.