Even though the British police has used police boxes since the 1920s, the BBC has the copyright of them for the TARDIS!

The BBC science fiction show "Doctor Who" features a time machine disguised as a police box. A police box is a telephone booth located in a public place for members of the public to contact the police and for the police to use. These police boxes could be found all over London, and in the show, the time machine broke and was stuck disguised as this box.

Over time, this police box became famous and it was associated more with "Doctor Who" than with the actual police. As such, in 1996, the BBC applied for a trademark for the blue police box so that they could use the image on "Doctor Who" merchandise. In 1998, the police filed a formal objection claiming that they owned the rights to the police box image.

In 2002, the Patent Office ruled in the BBC's favor. They said that the police had never actually trademarked the police box image so it was available for "Doctor Who." The series was revived in 2005 and continues to feature the police box.

(Source)