Ronnie Stock is the wealthy man of the village of Melstone. He raises (and races) horses, and his house (and private horse Gallops) is built right across the boundary of Andrew Brandon Hope's field-of-care.
Ronnie doesn't play a big role in this novel, but he is in it tangentially. He is the employer (on Wednesdays, Thursdays, and Saturdays) of Stache, who exercises horses for him and keeps a record of racing statistics in his computer for him. He is the person who is chosen to open the village Fete, which turns out to be the location for one of DWJ's big confrontation/resolution scenes. And it's interesting to learn that he is no relation to either Mr. Stock the gardener or Mrs. Stock the housekeeper. He is from another branch of Stocks entirely.
Kind of a dull but affable person, and neither bad nor good news.