Great Britain took the lead in international riding competition last night as Robert Smith raced Sanyo Shining Example over a 10-obstacle course to win the $7,500 international-open jumping class at the opening session of the 26th Washington International Horse Show at Capital Centre.

Four-person riding teams from Canada, Great Britain and the United States are competing in jumping events during the eight-day show.

Smith, 23, a professional rider from Bradford, West Yorkshire, guided the 12-year-old Dutch gelding over the time-first course in 39.74 seconds without fault. The riding victory gave him seven points and the early lead in the international riders' standings.

Sanyo Shining Example is the same animal Smith loaned his brother Stephan to ride when he represented Great Britain during the Summer Olympic Games in Los Angeles.

Only a fraction of a second slower in a field of 32 entries was Alwin's Ace with Michael Matz aboard. The 8-year-old gray gelding owned by Pablo Ceballos of Caracas, Venezuela, was clocked at a clean 40.28 seconds.

Matz, of Collegeville, Pa., the leading rider on the Mercedes American Grandprix circuit with 113 points, is riding as an individual and picked up five points and the lead in the national rider standings.

Kalmia des Mesnils, shown by Norman Dello Joio, 28, of South Salem, N.Y., was third in 40.35 seconds without fault, followed by Canadian Equestrian Team member Gail Greenhough aboard Astragalin in 43.07 seconds. The clean fourth place gave the Canadians second place in the international team standings with three points.

Another Canadian rider, Danny Foster, aboard It's Casual, placed eighth in a clean 53.66 seconds, and Americans riding as individuals took fifth, sixth and seventh places.

United States Equestrian Team members Joe Fargis, Melanie Smith, Conrad Homfeld and Leslie Burr, all of whom were part of the gold-medal team in Los Angeles, either knocked down rails for faults or took too much time to complete the course.

Dello Joio trails Matz in second place with four points.

International-open jumping continues this evening with the $5,000 Gen. Dwight D. Eisenhower Memorial Perpetual Trophy.

In later competition, Woody, a 9-year-old bay gelding shown by owner Christa Bartel of Great Falls, Va., was named local children's junior hunter champion and Farnley Cotillion, a 7-year-old chestnut mare ridden by owner Alison Grewell of Fulton, Md., was pinned champion in the local pony hunter under saddle class.