It had no name tag or collar on it so I took it home with me while I tried the phone. I couldn't get through to the cat and dog home, local police station or council services because they were all shut for the night...
I decided to keep it in overnight and take it to the local police station in the morning to see if anyone had reported it missing. Unfortunately my own dog started chasing it and barking with it. I couldn't keep it in the house as I have neighbours above an below me and this would have went on all night. I took it back to the park and let it follow a scent if appeared to recognise. When one of my previous dogs ran away it came home itself so I figured this one would too although I felt bad letting it go.
This morning, to my surprise, the dog was still under the park bench! I was on my way to work so I let it jump in my car and took it to the police this morning. They will check to see if it has been reported missing and, if not, send it to the cat and dog home. It is sure to find it's original or otherwise good owners there.
If you own a dog please make sure it has a collar and some sort of identification details - also get it chipped with your details. I would have phoned the owners myself and drove it round for them...