Who is Horatio Welham from All About Love and what is their importance?

Horatio Welham is the friend and mentor of Lucifer's who is murdered for the rare collector's item he has discovered. Horatio leaves Lucifer his estate and the example of a couple completely in love with each other. From the beginning, Lucifer is taken by the garden that Horatio learned to cultivate. He knows that Horatio grew it to remember his late wife, Martha. Lucifer dwells on how their relationship was and sets it as the example that he wants his to follow.