Cctv cam installed inside home pointing outside.?

Can anyone tell me if it is legal to have cctv from INSIDE of my home looking out onto my car and summerhouse as recently I have been bothered with petty theft i.e. hub caps stolen several times and car motif twisted and also would like to keep check on back and front door as I live alone. To expensive to get work dine on outside and heard that I would need permission for this, is this so? help please. A thank you in anticipation