That is a great piece of work to read through and makes you want to track some of things we've all seen over the years in trees.
David is a really good bloke even if he does like the collarless shirt a bit too much, his presentations are always really great to listen too amusing and packed with info.
He was out here earlier in the year helping another good Arb guy Mike Ellison delivery seminars on Mikes work Quantifiable Tree Risk Assessment QTRA and VTA maybe some of you caught them on tour?
Here's the site with a couple of docs that lay out the basic bones of the QTRA method
http://www.qtra.co.uk/cms/?section=39
For more in depth work on the changing way some Arbs in UK are looking at trees the environment and everything check out the docs at this site
http://www.arborecology.co.uk/articles.htm 
again heaps of stuff there to stimulate the grey matter
esp the two papers on decaying wood and pruning in context... boy theres food for about 50 threads there.
SF