John's recent TV credits include BBC Wales’ TV series Hidden (Craith), the BBC Wales successful crime series Hinterland, set in Aberystwyth, and the documentary Andrew Marr’s Great Scots: The Writers Who Shaped a Nation. Recent film credits include the feature Steel Country (A Dark Place), starring Andrew Scott, and the 2018 Gareth Evans film Apostle, starring Michael Sheen and Dan Stevens.

John's music has been performed and recorded by the BBC Concert Orchestra, BBC National Orchestra and Chorus of Wales, Royal Liverpool Philharmonic Orchestra, City of Prague Philharmonic Orchestra, Westminster Abbey Choir, BBC Singers, London Brass, Serendipity, Only Men Aloud, Vivace Singers and his own Ensemble.

His music has been described as "hauntingly atmospheric" (The Observer) "unique" (the Guardian) "witty" (The Independent) "gripping and intensely theatrical" (Opera Now) and "energetic, instinctive" (The Times). The Guardian wrote about John's music for National Theatre Wales' universally praised 'The Persians', saying "4 Stars - what is impressive... is the totality of the experience.... superb production, with atmospheric music by John Hardy."

His orchestra suite 'Blue Letters from Tanganyika' was commissioned and recorded by the BBC National Orchestra of Wales and released on John's own label Ffin Records. It has been remixed by Culprit One and described as "powerfully cinematic" by the South Wales Echo and as "immediately engaging... bright and colourful" by Gramophone Magazine.

John studied at Oxford University and Guildhall School of Music & Drama. Since 2010 he has worked as Head of Contemporary Music at the Royal Welsh College of Music & Drama.