Thanks, Robb - I'm frustrated, but have spent some time using different audio software and it's not sounding much better.
There was one other Brit there with me, plus a local guy who had taken us to see Edward. At the time I wasn't thinking of making clear recordings - just getting the salient points so I could write about him. I reckon Edward was sat about 10 feet away and recall sitting on the floor - not on chairs, around a table. This was over 20 years ago.
Here's another edited audio clip which will form the start of the finished YouTube interview - it gives a better idea of how it sounds...
Edward Hamilton 3.mp3