Chasing leaks

I have been chasing a waterleak a for a few days. This leak is where a new Main and Services have been installed and the old main abandoned. Now here is the problem, this is an old serviceline on the abandoned main and it has water coming from it. What I have to do now is dig down to the old main cut a section out, see which direction the water is coming from and camera up the main and see iif we can find where the water is entering the main.