Ewan grew up in Kent playing cello and double bass. He moved to London in 2002 to study music at King’s College, where he returned in 2008 for his PhD, supervised by George Benjamin and Silvina Milstein. Between those spells in London Ewan achieved distinction in his MPhil at Cambridge University, and was subsequently appointed as Composer-in-Residence with the CU Music Society in 2012. Ewan held an Associate Lecturer position at KCL until 2015, and is now Director of Music at Churchill and Murray Edwards Colleges in Cambridge, where he directs the Inter Alios Choir and seeks to broaden the programming and participation of University music making.

Ewan's music has been awarded several international composition prizes including the New York based Counterpoint Competition, the Forme uniche Competition in Adelaide and the Italian Mare Nostrum Competition. His works have been performed by ensembles and soloists including: London Symphony Orchestra, Britten Sinfonia, Fretwork, Küss Quartet, Fukio Ensemble, Lontano, Ensemble Matisse, Consortium 5, The Hermes Experiment, Mercury Quartet, Dr K Sextet, Anton Lukoszevieze, Gaby Bultmann, Thomas Gould and Clare Hammond. Ewan enjoys collaborations with other artforms, and has worked with theatre maker Andrew Dawson, choreographer Katie Green, and Physical theatre company Bottlefed, filmaker Sebastian Barner-Rasmussen, and artists Issam Kourbaj and Tim A Shaw.

Ewan directs the Wilderness Orchestra and choir, which perform his orchestral arrangements of artists such as Radiohead, David Bowie, Queen, Aphex Twin and Nina Simone. They have performed with a number of collaborators including Charlotte Church, Kate Nash, London Contemporary Voices, La Fura del Baus, Camille O'Sullivan, Jessie Ware, Francesca Lombardo, beatboxers Shlomo and Reeps One, and actors Olivia Williams, Rashan Stone and Jack Whitehall.

Ewan is an enthusiastic teacher and enjoys working with young people. He mentors students of the Aldeburgh Young Musician scheme; supervises at Cambridge University; delivers workshops for Cambridge Music Outreach and judges the East Anglian Young Composer of the Year Competition.

With the London Symphony Orchestra during the 2016 Panufnik workshop