Given that one of the jobs I do (as a traffic survey supervisor) involves recording number plates of vehicles (and linking them to their movements), both manually and via video cameras, I sincerely hope that it's legal!
As NJ states, with only a very few exceptions, it's lawful to take a picture of anyone, or anything, as long as the photographer is:
(a) on his own property ; or
(b) on property where he has been given permission to take photographs ; or
(c) in a public place (such as in the street).
For example, it's perfectly legal to stand in the street and take pictures of people in their front gardens or (through their windows) inside their houses.
Even if I was to walk into your garden and to start taking photographs of you there, I would still not have committed any criminal offence. (Trespass and the unauthorised taking of photographs in a private place are both purely civil matters).
Chris