It is the manoeuvre that BP hopes will signal the beginning of the end of the Gulf of Mexico oil spill.
The energy giant has put a containment cap on top of the damaged wellhead, hoping it will successfully stem the devastating leak.
BP is under increasing pressure to get the job done after a number of failed attempts.
This time around, things have run far from smoothly. A saw was unable to sever what is left of the pipe, meaning giant shears had to be brought in. For now, BP’s boss is remaining prudent.
“None of this has ever been done so there is always risk,” said BP Chief Executive Tony Hayward.
“The risk is reduced but there is still risk as to whether or not it will be fully successful and the next 12 to 24 hours will give us an indication of how successful this attempt will be.”
BP does not expect to be able to fully halt the oil flow until August when two relief wells are due for completion. Today, President Obama will make his latest visit to the Louisiana Gulf coast to view what has been described as the worst environmental disaster the US has ever faced.