Her first professional produced work as a writer was an adaptation of Hans Christian Andersen's The Snow Queen, commissioned by Orchard Theatre Company in 1989. "The Mysterious Mr Love" was produced in London's West End in 1997. Her most recent play Tryst opened off-Broadway at the Promenade Theatre, on April 6 2006, and has subsequently been produced in Houston, Los Angeles and Montreal.

Leach's theory of a 'Carroll Myth' created a furore when first suggested, and continues to divide scholars, although in recent years the idea has been gaining ground, with authors such as Carolyn Siger offering it support. However, authors like Morton N. Cohen, Donald Rackin and Martin Gardner continue to downplay or dismiss her importance. Cohen, who is also a Dodgson biographer, repudiates Leach's position as being simply a plea for the defence, and, in a recent article in the Times Literary Supplement labeled Leach and her supporters as 'revisionists' attempting to rewrite history.

In 2004 Leach founded the Association for New Lewis Carroll Studies,that aims to promote reassessment of Carroll's life in light of the alleged 'Myth'. Its membership,as of 2010, includes scholars such as Hugues Lebailly, Carolyn Sigler, Sherry L. Ackerman, John Tufail and Cristopher Hollingsworth.