[11] In 1994, words by Mackmin accompanied photographs by Patrick Sutherland in a Maidstone exhibition exploring the changing face of Kent.
[4] These included George Barker, Oliver Bernard, Glen Cavaliero, Dick Davis and Ida Affleck Graves.
[4] Other contributors included Margaret Atwood, Carol Ann Duffy, Gavin Ewart, Maggie Gee, Miroslav Holub, and Alexis Lykiard.
[20] With fellow poet Matt Howard, Mackmin founded the RSPB & The Rialto Nature Poetry Competition.
[22] In 2023, Mackmin edited the anthology Poetry with an Axe to Grind: A Celebration of the One Hundredth Issue of The Rialto, described by the TLS as a "quirky affair".