Peter O'Toole and David Tennant portray the world's greatest lover in his nostalgic old age and his action-packed youth in a two-part drama based on the real life of Giacomo Casanova, the infamous 18th-century lothario. Also appearing are Laura Frazer ( A Knight's Tale, "He Knew He Was Right") as the love of Casanova's life; Rupert Penry-Jones ( Match Point, Cambridge Spies) as his archrival for that affection; and Nina Sosanya ("Doctor Who") as a castrato impersonator who makes a big impression on Casanova. Casanova has good advice for those who would emulate him: listen to your lover.