In November 2011, seven people died and 51 were injured in a motorway pile-up involving dozens of vehicles. It was one of the UK's worst ever road traffic accidents.
Despite reports at the time of fog and bad weather affecting the motorway, a police investigation suggested that the accident may have been caused by thick smoke from a nearby firework display organised by Taunton Rugby Club.
After determining that there was insufficient evidence to charge any driver or the rugby club, the organiser of the firework display, Geoffrey Counsell, was charged with seven counts of manslaughter.
These charges were dropped earlier this month and replaced with a single charge of failing to ensure the safety of others under Section 3 of the Health and Safety at Work, etc. Act 1974. The new charge carries a maximum sentence of two years in prison.
The prosecution has stated that its decision to backtrack follows consultation with an expert on negligence, and new evidence coming to light. It has not indicated what this new evidence might be (and is unable to do so while the health and safety proceedings are ongoing). However, media reports suggested that there is evidence that fog, rather than smoke from the fireworks, may have been to blame.
There has also been some criticism of the motorway fog lights, which were not automated and which had not been turned on at the time of the accident. Given these uncertainties, it is not surprising that the prosecution is not pursuing manslaughter charges.