The names in the title of the piece refer to Allegra Mostyn-Owen and Boris Johnson. Allegra Mostyn-Owen is the only daughter of the Italian poetess Gaia Servadio and the historian William Mostyn-Owen. Hans Werner Henze composed this Duetto concertante as a gesture of friendship towards the mother on the occasion of Allegra's marriage to Boris Johnson in 1987. Hans Werner Henze's output is primarily dominated by large-scale, representative musical genres with a richly differentiated instrumental tonal palette: opera and other forms of musical theatre works, ballet, solo concertos and cantatas and also music for large-scale orchestra or chamber ensemble. In contrast, the chamber music works which Henze has composed throughout his entire compositional career right up to the present day have always remained somewhat on the sidelines. Many of these chamber music works had been composed for specific occasions, chiefly to honour figures who had accompanied him on longer or shorter stretches o f his journey through life.