Hannan's work as a playwright has been produced by the Royal Shakespeare Company at the Barbican (1991) and by Sir Peter Hall at the Old Vic in London (1997) as well as by the National Theatre of Scotland in its inaugural season (2006).
 
He often creates big central roles for women.  The Guardian hailed Elizabeth Gordon Quinn as a "monstrous and magnificent heroine".

The same critic described the central character of Shining Souls as a kind of Mother Courage cum Marilyn Monroe of the post-industrial wastelands.  
 
Four of his plays have had their world premiere at the prestigious Traverse Theatre in Edinburgh, including Elizabeth Gordon Quinn and the award-winning Shining Souls. His 1990 play The Evil Doers was produced by the Bush Theatre in London and won numerous prizes including a Time Out Award, and in 2001/2 he was the Judith E. Wilson Visiting Fellow in Drama at the University of Cambridge.
 
In 2008 his first novel Missy was published in the UK and the US.