Deer in Garden

Living in a rural area I often see deer in the field behind my house. Late yesterday afternoon there was a deer in my garden - that part of the garden is very sheltered and I have no idea how it got in (the hedge between the garden and the field is very wide and around 6ft tall). I decided to leave it alone (I didn't even close the blinds in the conservatory in case the movement startled it) and the last time I looked out it appeared to be settling down for the night under the hedge. It was wonderful to see such a lovely creature so close but I found myself worrying about it all night and hoping it would find it's way back to the field

I can't see it from the windows now but I haven't ventured out to check the couple of "hidden" spots in the garden.

Now if it is still there - what do I do? Should I leave it or call someone to help get it back to the field, and if so, who do I call!