How can a local authority enforce repair to a boundary wall [UK law only, please]?

There are three walls in my town that concern me most.

1. There is a dry stone wall, about 1.25m in height, that has partly collapsed, owing to uncontrolled growth of vegetation. The wall fell away from the owner's land (a historic lane) into a public recreation ground, owned by the town council. The town council claimed that, as it was not the owner of the wall, it could not repair it, or even remove the fallen stones. My concern was about the danger that the rubble posed to the public, especially small children. Surely a local authority (either the same town council or the unitary authority) has enforcement rights to get the vegetation cleared and the wall repaired? The wall is shown in the following video [from 00:07 to 02:17].

http://www.youtube.com/watch?v=pK9hFGiv06E

Eventually the town council pushed some of the wall the other way, and fenced off the area, exactly as it claimed it would in a reply to a Freedom of Information request that I made.

http://www.whatdotheyknow.com/request/34140/respon...

To me, that does not seem like a sensible answer. Instead of making the town's park safer, the council has reduced the amount of land available to the public.

2. In another part of the same recreation ground, there is a much higher wall that is slowly disintegrating, with stones falling into the park. It is shown in the same video [from 03:12 to 04:44]. Some of the fallen rubble has been removed, and the area, which was a small copse, has had some trees removed, in order to make the danger area more visible from outside the copse. Again, I believe there must be some enforcement right, and that the town council should have an interest in getting the wall made safe, because of the risk to the public, and the need to grant access to the area for works to be carried out.

3. The third stone wall, maybe about 70cm high, is in another part of town entirely. A section of the top of the wall has come loose and has fallen (or been pushed) around, so that one end lies on the ground and the other end lies over the rest of the wall. I suspect that responsibility for the wall lies with the unitary authority, as there is a tarmaced footpath at one side of the wall and a street at the other side. Again it is shown in the video [from 09:10 to 10:28]. I would have thought that the unitary authority was obliged to make this safe, but I welcome informed opinion.

I intend to produce an update video shortly - the filming has already been made. Credit and thanks will be given to anyone, whose reply is used in the video. So there's a bonus - a chance for (very limited) fame!