 With Walter's editing complete, composer Barry Gray recorded the score in six sessions between 9 and 11 October at Anvil Studios near Denham in Buckinghamshire. To achieve proper symphonic sound, an orchestra of 70 musicians, aided by Gray's own electronic effects, was organised. The Band of the Royal Marines' rendition of the "Thunderbirds March" which accompanies the end credits of the film was recorded in one morning under the supervision of Gray and conductor Lieutenant Colonel Vivian Dunn at the Royal Marines School of Music in Deal, Kent. Three weeks were then allotted for visual wrap-up work, the insertion of the opening titles and minor animation, sound editing and dubbing. On its submission to the British Board of Film Classification in November, the film was awarded a U certificate.
