I know that this is late, but I was prompted last week to ascertain the status of Mr Kletz. C’est la vie.
Trevor Asher Kletz, OBE, FREng, FRSC, FIChemE (1922–31 October 2013) was a prolific British author on the topic of chemical engineering safety. He is credited with introducing the concept of inherent safety, and was a major promoter of Hazop.
Here’s an obituary from The Guardian.