The Flixborough explosion was the largest-ever peacetime explosion in the UK. There were 28 fatalities as well as near-complete destruction on the 24ha plant. An official Court of Inquiry was immediately established and charged with the responsibility of determining the cause(s) of the disaster and the lessons to be learnt. Reviews are made here of the evidence and arguments behind an alleged 8 in initiation to the event and briefly that of the Court's determination of failure-the simultaneous failure of two 28 in bellows attached to a temporary 20 in dog-leg pipe bridge. Both cases are seen as flawed. The only credible hypothesis appears to be one that involved the failure, most probably by fatigue, of only one of the two bellows attached to the dog-leg-this then buckled, sealing the lower reactor. The dog-leg later collapsed by the blast. This process resulted in a much smaller explosive release than either alternate hypothesis and thus may have consequences for reportable inventories and process safety. The investigation employs NIST FDS CFD analyses of the potential releases, fires and their influence. (C) 2007 Elsevier Ltd. All rights reserved.