The message from Steve contains these words:
Watch out for the effect of wind. I dug out an 18 foot Alder tree today and the wind gusting to 60 mph proved of considerable help but if you are sawing through a 30 foot tree well above ground level you really want a calm day.
I have a leylandii hedge to the East of my garden which I try to keep less than 15 feet high. It makes an excellent windbreak and as it runs North/South shading is not really a problem.