--For years afterwards the farmers found them - the wasted young, turning up under their plough blades.- So run the blunt, grimly beautiful opening lines of the Welsh poet Owen Sheers-s elegy for the men, 4,000 of them from the 38th (Welsh) Division, who were killed or wounded in the Battle of Mametz Wood in July 1916- Sheers revisits that chapter of carnage in a stirring, sprawling promenade show- He draws on the writings of two survivors in particular. One is the poet David Jones whose fractured, enervated, modernist response to his war-time experiences, In Parenthesis, was hailed as a -work of genius- by TS Eliot. The other key influence is the writer Llewelyn Wyn Griffith- driven to wondering how the sun -could shine on this mad cruelty and on the quiet peace of an upland tarn near Snowdon-... We end up in dark woods and a place of numb desolation, bombarded by words that pierce the heart and vignettes that capture the stomach-churning sacrifice- The finest commemoration