The Flixborough explosion was the largest-ever peacetime explosion in the UK. There were 28 fatalities as well as the near complete destruction of the NYPRO plant in North Lincolnshire by blast and then fire. An official Court of Inquiry was established and charged with the responsibility of determining the cause(s) of the disaster and any lessons to be learnt. This paper reviews the disaster, its investigation and inquiry, its attributed cause, and an alternative possibility, and this redraws the lessons to be learnt for modem chemical plant design and accident investigation. The reanalysis suggests that the failure was caused by a complex two-step mechanism that resulted from the initial failure of only one bellows, a release of about 10-15 tonnes of cyclohexane, and the detonation of the consequent vapour cloud with an explosive effect of some 280 tonnes of TNT. This is compared with the single-step failure process reluctantly acknowledged by the Court; the amount of release accepted, 40-60 tonnes of cyclohexane, and its explosive effect, 6-16 tons of nitroglycerine. The results should be of interest to industry, regulators, and loss prevention and risk assessment specialists.