The slide in question briefly appeared on the Oil Spill Commission's website in error, but was quickly retracted. The newspaper a screenshot of the slide, which showed at least eight "risky" steps that BP and its partners Halliburton and Transocean were judged to have taken in order to save time. Each step was "unnecessary", experts concluded.

Advanced cement modelling software, provided by BP's cement contractor Halliburton, had highlighted with the well, saying more centralisers - which are used to provide space around the oil pipe casing as cement is poured in - needed to be added to ensure safety.

BP initially ordered the extra centralisers. But when the devices arrived at the rig, engineers mistakenly thought they were the wrong type. BP decided at this point to continue with the project without the additional centralisers, taking other safety steps. It also decided not to rerun the cement modelling software, and questioned the accuracy of the technology.

As the drilling proceeded, Brian Morel, engineer at BP, wrote an email to colleague Brett Cocales, saying: "Who cares, it's done, end of story, we'll probably be fine".

The project had been running late. While the site was not fully functional it was still reportedly costing nearly £1 million every day to operate.