The opening music is a specially recorded version by Julian Joseph of the music which was used on Radio 4 for the previous two series of This Sceptred Isle: it's the opening of the Prelude to the Suite for Strings by Frank Bridge.
Bridge was born in Brighton and studied at the Royal College of Music in London from 1899 to 1903 under Charles Villiers Stanford and others. He played the viola in a number of string quartets, most notably the English String Quartet, and conducted, sometimes deputising for Henry Wood, before devoting himself to composition, receiving the patronage of Elizabeth Sprague Coolidge. He privately tutored a number of pupils, most famously Benjamin Britten, who later championed his teacher's music and paid homage to him in the Variations on a Theme of Frank Bridge (1937), based on a theme from the second of Bridge's Three Idylls for String Quartet (1906). Bridge died in Eastbourne.
Among Bridge's works are the orchestral The Sea (1911), Oration (1930) for cello and orchestra and the opera The Christmas Rose (premiered 1932), but he is perhaps most highly regarded today for his chamber music. His early works are in a late-Romantic idiom, but later pieces such as the third (1926) and fourth (1937) string quartets are harmonically advanced and very distinctive, showing the influence of the Second Viennese School.