Mike touched many lives with his work. NAG and NAG's community benefitted greatly because he gave freely his code to NAG from the very beginning. The more mature may remember the routine E04DCF, an implementation of his hybrid method for unconstrained optimisation. More recently his work on derivative-free optimisation led to E04JCF/e04jcc entering our Libraries as implementations of BOBYQA.
As a founder member of the IMA, Mike took an interest in the IMANA Newsletter and encouraged NAG to contribute regularly to that until the Newsletter's role was subsumed by the internet.
The Wikipedia page http://en.wikipedia.org/wiki/Michael_J._D._Powell gives more detail of Mike's many achievements.
He will be greatly missed by NAG, especially past and present colleagues who had the pleasure of knowing him personally. We pass on our love, condolences and very best wishes to his family.