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Early Breakfast with Jenni Falconer 4am - 6am
Actress will star as Effie Gray
Knightley has been cast as the wife of 19th century art critic John Ruskin who left her husband for the Pre-Raphaelite painter John Everett Millais.
The love triangle has been dramatized several times in plays and in an opera.
Emma Thompson is currently shooting her own film version, called Effie.