Karl studied music at Goldsmiths, Morley and City Lit and attended the Stratford East Musical Theatre Workshop in 1999. His musical Release The Beat, was produced by Arcola Theatre in 2004 and directed by Mehmet Ergen. The story is based on Midsummer Night’s Dream and set in London’s hip-hop and house clubs. This was followed by Goodbye Barcelona, the story of the International Brigades. This was produced at Arcola in 2011 and directed by Karen Rabinowitz. Subsequently produced in Barcelona in 2013 and winner of Best Spanish Musical 2014, the musical opens in Madrid in November 2016, is being revived in Barcelona and being developed in Mexico City with a first reading in November 2016. His new musical The Queen and I is being developed at the Arcola where it had a second workshop in August 2016, directed by Mehmet Ergen. The musical had a first reading in August 2015 as part of the Grimeborn Festival, directed by Kate Golledge.