Not strictly speaking an opera, King Arthur, or The British Worthy is a 'semi-opera'. Semi-operas were dramas in four or five acts, with lengthy musical sections. The main characters only speak, and the musical narrative is the preserve of the minor characters - nymphs and such like. John Dryden, who provided Purcell with the libretto in 1691, commented that 'Purcell was the equal to the best (composer) abroad', and that in King Arthur 'my art on this occasion, ought to be subservient to his'.

The story depicts the battles that the Britons, lead by Arthur, fight and win against the Saxons and their leader Oswald. Urged on by the evil spirit Grimbauld, the Saxons resort to ever more cunning tactics. Arthur magnanimously forgives the Saxons upon his victory, and the work ends with a patriotic masque praising Britain, her people, values and nature.

Purcell provided a vivid score, with some of his finest music, and the 'Frost' scene in Act 3 foreshadows Vivaldi in many ways. It also provides the inspiration for Michael Nyman's music for the Peter Greenway film The Draughtsman's Contract set in the 17th century.

Further information
- Recording made in 1991
- 'He (Pinnock) has an orchestra of glittering skill, often used with considerable delicacy ... sounding wonderfully persuasive on plucked instruments ... His soloists are also good, all of them sometimes exceptionally so.' Gramophone
- Booklet contains an introduction to the opera, and a comprehensive synopsis of the plot