Sovereign Secrets: Diplomacy is Deadly. Desire is Dangerous. (Shared Secrets Book 1) by Livia Huntingdon-Jones

She commands nations. He commands her safety. Control is about to shatter. Ambassador Isabelle Dubois lives by the rules – elegant receptions, calculated smiles, and the suffocating weight of representing France on London's elite stage. Her world is perfectly curated, entirely predictable... until him. Kaelen Jones. Her new head of security. Lethal, infuriatingly controlled, and dangerously perceptive. He sees the cracks in her gilded cage and the vulnerabilities in her security. He's the guardian she never wanted, enforcing rules that feel more like chains. In a world of sovereign secrets, the most dangerous lies are the ones they tell themselves.