The Runaway Heart by Barbara Cartland

At the tender age of twenty-one, demure beauty Karina Burke looks considerably younger. Having lost her parents at an even younger age, she is beholden to her imperious Aunt Margaret and Uncle Simon, who have taken her in at their sombre mansion, Letchfield Park. Now they are insisting that Karena should marry her cousin, Cyril, and, as if the fact that she does not love him is not enough, he is also mentally deficient and repellent. With the invaluable assistance of her charming Cousin Felix, she runs away from her uncle and aunt and finds herself in the middle of the sophisticated Social world that revolves around her new employer, the immensely handsome, famous but unfriendly City magnate, Garland Holt. And, although Garland’s incorrigible cousin, Jim, declares his love for her, as does the increasingly suspect Cousin Felix, Karina is aghast to discover that it is only the aloof and unreachable Garland Holt that her runaway heart desires.