The Cantarell oil field, in the shallow waters of Campeche Bay, is regarded by Mexicans as their crown jewel. It is the second largest oil field in the world by production, behind Saudi Arabia's mammoth Ghawar oil field, pumping 2.2m barrels a day, the same amount as all the Kuwaiti fields together.

For that reason, Mexicans were recently dismayed when Petróleos Mexicanos, the state oil company, said that the field's production would decline this year, signalling a trend towards its depletion.