Since April 2018, Martinson has been the Marjorie Deane Professor of Financial Journalism at City, University of London.

[1] Raised on the Isle of Dogs in East London, Martinson attended George Green's Comprehensive and a local sixth-college.

[5] After a period working as the FT's Wall Street correspondent she joined The Guardian in May 1999,[6] and remained in New York as the US business editor.

[8] Martinson was appointed as The Guardian's media editor in 2007, and assumed the post in January 2008 after returning from maternity leave.

[10][1] In early 2018, Martinson was appointed as the Marjorie Deane Professor of Financial Journalism at City, University of London.