Thanks all for IDing the snake. The heron did put the snake down several times but as far as I could tell it was alive when he swallowed it. Unfortunately I only had a 400mm lens (equiv to 640mm with crop factor) and it was all happening a long way from me.
Below is a full frame shot of the action taken on the Canon 7D with 400mm lens.
Bob
![](http://farm3.static.flickr.com/2717/4406306542_0a8f014e9a_o.jpg)