Plot: Tom Service reaches the 20th century on his route through Masterworks at the Proms, by way of Jean Sibelius and William Walton. Canadian violinist James Ehnes performs Walton's striking violin concerto, and Thomas Sondergard conducts the National Orchestra of Wales in two works by Sibelius - the transcendent tone poem The Swan of Tuonela, and his Fifth Symphony with its memorable, ecstatic 'swan theme'