The UK supermajor bought the LNG shipment from another gas supplier, according to a company spokesman.

"We've sourced it from a third party," he said, but refused to name the seller.

The Maran Gas Asclepius is the 33rd LNG tanker to dock at the Isle of Grain facility run by National Grid since it opened in summer 2005.

LNG coming into Grain, still the UK's only LNG import facility, is re-heated into normal gas and pumped into storage ready for release to the UK's gas network, which pipes it to consumers.

It