Sam, riding his long-time four-star campaigner Happy Times, posted a score of 40.2 which heads the field by more than 5 penalties.
“I’m really please with him,” Sam told H&H. “He is a good old campaigner for me. I know he can do a beautiful test and today he came out and performed.”
Britain’s Piggy French and Westwood Mariner are in second on 45.8 with Sarah Bullimore and Valentino V are in third with 49.5.
Westwood Mariner divided the judges with the judges at E and C awarding 72% and 71% respectively, but judge C giving 65%.
“He can be a horse a bit like Marmite,” Piggy told H&H. “He has not got the best conformation. He is very difficult to get his neck out and his nose truly out.
“I think he is better, but some people still think he is a bit short in front.”