Hannan's work as a playwright has been produced by the Royal Shakespeare Company, the Old Vic, Shakespeare's Globe and the National Theatre of Scotland.
His most recent play What Shadows opened at Birmingham Rep in October 2016 and was described by the Daily Telegraph as "the most provocative theatrical act of the decade."
His 1990 play The Evil Doers was produced by the Bush Theatre in London and received a Time Out Award among other prizes, and in 1996 his highly-acclaimed Shining Souls won him a nomination for Lloyds Bank Playwright of the Year.
In Scotland he is best known for Elizabeth Gordon Quinn, which is widely studied and was re-mounted by the National Theatre of Scotland in the first year of its existence.
In his plays he often creates big central roles for women. The critic Joyce McMillan, writing in 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 and called the play a "funny and serious postmodern masterpiece."