In practice it means diners at the certificated Compass restaurants will see an MSC logo next to the appropriate dish and will be able to order it safe in the knowledge it comes from well managed fish stocks.
It initially covers five Compass clients, including Oxford Brookes University, Westminster Schools, the Wellcome Trust and investment bank Lehman Brothers, but is likely to be rolled out to more.
Rupert Howes, chief executive of the MSC, said: "This is a true first: Compass is one of the biggest food service organisations in world.
"Chain of custody certification is a powerful demonstration of Compass's commitment to sourcing certified sustainable seafood."
By Chris Druce
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