Duncan, who left Rolls-Royce after three years in April (PRWeek 9 April), joined Grandfield as a senior consultant last week and will work on a part-time basis.
He is to act as strategic counsel to Grandfield's major clients, though his exact responsibilities have yet to be agreed with Grandfield chairman Charles Cook.
Duncan's particular expertise is in the natural resources sector. In the 1980s he and Cook worked together at BP, as director of European PR for the exploration business covering the North Sea and head of corporate media relations respectively.
Duncan also spent ten years at nuclear fuels reprocessing company BNFL.
Becoming director of public affairs in 1995, his remit expanded to cover government and media relations, publicity and marketing, and community affairs before he resigned in 2000 (PRWeek, 15 December 2000).
Duncan said that his move from BNFL to Rolls-Royce and now to Grandfield had been motivated by a need to maintain a more favourable 'work-life balance'.
Grandfield natural resources clients include Ashanti Goldfields, which the firm last year advised on an £817m merger with AngloGold.