Hartley was an amateur boxer for York and Yorkshire in the late 1970s and early 1980s. He trained at the London Academy of Music and Dramatic Art (LAMDA) from 1981-84. After a number of theatre performances and many commercials, he was interviewed for the role of James Bond in 1985, but was turned down because of his young age. For a 6-month period in 1990, he turned to labouring on a building site when acting jobs were sparse, but a surge of TV and film roles would soon follow.

Hartley is also a voice over Artist having voiced TV documentaries and commercials and has been the station voice of Talksport for 18 years. In 2002 he was nominated for 'Sexiest Male' at the Inside Soap awards 2002. He was also nominated for a 'Broadway world' west end award for best takeover for 'Bill Sikes' in 'Oliver!' in 2011.

He has worked opposite notable actors on film Including Marlon Brando, Catherine Zeta-Jones, Benicio del Toro, Lauren Bacall, Kristin Scott Thomas, Woody Harrelson and Jon Voight. His films include [Allies} 2014 Ruby Strangelove (2015), Robocroc (2013), Jetstream (2012), The Walker (2007), A Dog of Flanders (1999), Christopher Columbus: The Discovery (1992), Split Second (1992), Young Toscanini (1988). Hartley's extensive theatre work includes reprising his role as Bill Sikes in the West End Musical Oliver! in 2009-2010 for Producer Cameron Mackintosh, the third time Hartley has played the role since being cast by Director Sam Mendes in 1996 and recently played a leading role in 'Fit and Proper people' for the Royal Shakespeare company.