Born in Zimbabwe, Duncan studied horticulture in Northern Ireland and landscape design in Wales. He developed a career as a professional gardener and landscape designer which took him to a number of countries in Africa as well as Jordan, Bermuda and France. He joined Arundel Castle in 2009, the ancestral home of the Duke of Norfolk.
He called receiving the medal "truly special and wonderful".
Since he arrived at Arundel Castle, Duncan has designed a unique Stumpery Garden and created one of the country’s largest annual tulip festivals, held every spring.
He said: "On meeting The Duke and Duchess of Norfolk, their enthusiasm, drive and passion to develop the castle gardens further was of great appeal. The old car park had just been transformed into the Collector Earl’s Garden and I could see that there was enormous potential to work with their graces to develop further areas of the castle gardens and structures."
In addition to the Stumpery Garden, Martin has also developed the castle’s gardens with the design of new tropical borders, a redevelopment of the English herbaceous borders, creation of a new wildflower garden and a thatched roundhouse.