This is a movie I remember watching as a kid in the mid 70`s. As far as I can remember it was filmed in black and white so not sure if it was filmed in the 50`s or 60`s. I think that the main character was possibly a spy who was following someone to a secret meeting house in the country. Not sure if it was a British film but I seem to remember they were driving a Jaguar. The thing that stands out was the country road that led to the secret house had a large tree across the road blocking access. The main character who was tailing someone observed that the tree could be raised and lowered by a press of a hidden button located on the tree or the side of the road to gain access. This mechanical tree was designed to only allow access to the house where a secret meeting took place that was observed by the main character through a window .
Sorry I know its not much to go on but unfortunately its all I remember. Thanks

Edited question