As you can see in the photograph below, the path takes a lot of water and if left to it's own devices heavy downpours can cause serious damage to a stone footpath. This photo was taken before we built an additional two drains higher up the path so the next time we have torrential rain the majority of the water will be removed before this point.
The problem we've had with fixing the drainage is that there's a dry stone wall located right at the end of the drain stopping the flow of water. In the next photograph you can just make out the drain (halfway between the shovel and sledgehammer) coming to an abrupt end when it reaches the wall.
So to allow the water to run away from the path we've had to take the wall down and incorporate a gap in the wall at the end of the drain. The following photo shows the wall after we've started to rebuild it. Putting in these drainage gaps has turned out to be a bigger job than expected. As the wall was in a poor state of repair, once we started taking it down it had a tendency to fall down on it's own. This created a much larger gap than we really wanted!