Grk Operation Tortoise (Josh Lacey) Paperback / softback

 When Tim discovers a man badly hurt on a beach, his sun-kissed relaxing holiday in the Seychelles takes on a more dangerous twist. He and Grk are the only ones, it seems, who want to know what happened. They find themselves speeding towards a well-guarded private island, and single-handedly foiling a dastardly plot threatening the local endangered giant tortoises.