On 12 July BP placed a new cap over the ruptured oil pipe in the Gulf of Mexico, hoping to stem the catastrophic flow of toxic crude once and for all. Almost 13 weeks after America’s worst environmental disaster began with a deadly explosion on the Deepwater Horizon rig, the end is finally in sight as engineers lower a device called the “Top Hat 10” from a surface ship.

As of 2000 GMT, the giant valve system was 40ft away from the pipe with BP officials saying it should be latched on by the end of 12 July, allowing vital tests on the integrity of the well to begin. “The best-case scenario: the pressures rise to the point we anticipate they would,” BP chief operating officer Doug Suttles told journalists. “We’d likely be able to keep the well shut in.” If the pressure reading is too low, it would indicate a leak somewhere in the casing of the well, which extends 13,000ft below the sea floor.

The valves would then have to be reopened and containment operations would have to resume as crude could be forced up to the surface outside the casing of the well, spawning a whole new kind of disaster. Mr Suttles said the integrity test could take anywhere between six and 48 hours, meaning the government and BP will likely decide whether the valves can stay shut, and the well is sealed, by this week at the latest.