British Emerald, the first GEM class ship, was delivered in July 2007. The second, the British Ruby was delivered on 1st July 2008 and the third, the British Sapphire was delivered on 1st September 2008. final GEM class liquefied natural gas carrier (LNGC), British Diamond was delivered on 20 October 2008
These ships can carry a cargo of 155,000 cubic metres of liquefied natural gas (LNG). These vessels are equipped with a dual-fuel diesel-electric (DFDE) propulsion system that increases their fuel efficiency and reduces fuel costs and Greenhouse Gas emissions. The dual-fuel technology allows the diesel engines to run on "boil-off" gases from the cargo tanks or on conventional diesel fuel, consuming about 40 tonnes per day less fuel than an LNGC of similar size with a conventional steam turbine propulsion system. Four diesel-electric engines provide greater propulsion redundancy and a bow thruster assists mooring operations.
The builder of these ships is Hyundai Heavy Industries Limited in Korea. They are British-flagged, with Douglas, Isle of Man as their port of registry. Their classification society is Lloyds Register. BP operates these ships, providing its own crews and provisions. They operate worldwide.