Gregory Stuart Lake was born in Poole, in Dorset County, England. His parents were Harry Lake, an engineer, and Pearl Lake, a housewife who played piano. He was 12 years old when he first learned to play guitar. After playing in various bands, he was invited by fellow Dorset native Robert Fripp to sing and play bass in the first lineup of King Crimson. Lake appeared on their first two albums. In 1970, he joined keyboardist Keith Emerson and drummer Carl Palmer to form Emerson, Lake & Palmer, which lasted until 1979. An attempted reunion during the 1980's resulted in the formation of Emerson, Lake & Powell, in which Palmer was replaced by Cozy Powell on drums. Lake started recording solo material in 1975. He also briefly replaced John Wetton in Asia, where he was reunited with Palmer.
Lake is survived by his wife Regina and their daughter Natasha.
According to Wiki, the top link above, Lake wrote Lucky Man when he was 12. It was recorded by ELP, with Keith Emerson (who died earlier this year) contributing the Moog synthesizer solo at the end.
Lake's solo release I Believe In Father Christmas, written with Peter Sinfield, reached #2 on the U.K. singles chart in 1975. It was written, not as a Christmas song, but to protest the commercialization of Christmas, something I can certainly agree with.