A Horse Rangers Association supporter swaps the saddle for her running shoes to raise funds for the charity.
Nicola Briggs, from Hampton, will take on the Brighton marathon on April 6 as a way of giving back to the East Molesey association.
Ms Briggs, who has previously completed 10km runs and five half marathons, has been a member of the Horse Rangers for more than 20 years, joining as a child and rising through the ranks to become a volunteer instructor in number one squadron.
Aside from her love of horses, Ms Briggs has a passion for sport and fitness, with a dream of completing a full marathon.
She said: “This is the year to make my dream come true whilst raising much-needed cash for my worthy charity as it celebrates its 60th year.”
To sponsor, visit uk.virginmoneygiving.com/NicolaBriggsBrightonMarathon2014.