Shell announced yesterday that Shell divers had successfully closed the relief valve from which oil had been seeping on Friday August 19th. The company also defended its safety record, which has come under attack since the incident.

The company also stated that no oil had been released since that point and continuous monitoring would continue to ensure no more leaks develop.

The Maritime and Coastguard Agency surveillance flight on Saturday found no oil on the surface.

36 concrete mats have been successfully laid on the flowline in a process to secure it to the seabed. This process will continue over the next few days.

The company said in a statement: "Safety is Shell's foremost priority at all times.

"As part of that commitment, in 2004 Shell initiated a $1.2bn (£728m) project to upgrade our assets in the North Sea. This has been completed.

"This year alone, we plan to invest approximately $600m (£363m) in our assets in the region.