He has written a number of other operas , The Martyrdom of St Magnus ( 1976 ) , The Lighthouse ( 1980 , his most popular opera ) , Resurrection ( 1987 ) , and The Doctor of Myddfai ( 1996 ) . He has written a number of other operas , including The Martyrdom of St Magnus ( 1976 ) , The Lighthouse ( 1980 , his most popular opera ) , and The Doctor of Myddfai ( 1996 ) .