Constitution Hill is set to encounter a serious trial of his lofty ambitions on the flat when he lines up for the William Hill September Stakes at Kempton Park this Saturday, this time under the guidance of a new rider, Billy Loughnane. The nine‑year‑old, once a superstar hurdler for Nicky Henderson, has won both of his flat starts since making the switch, but the Group Three event at the Sunbury course represents a considerable step up in class and distance. Up to now, Constitution Hill’s flat campaign has been piloted by top‑level jockeys Oisin Murphy and Ryan Moore. The British Horseracing Authority’s entry list for the weekend, however, shows Loughnane’s name attached to the Seven Barrows‑trained runner.

Loughnane’s agent, Tony Hind – who also manages Moore – confirmed the change, explaining that Henderson was happy to let the championship‑leading jockey step aside in favour of the younger rider. "His first choice was Ryan, who is currently riding in America," Hind said. "So I offered Billy, who is definitely there riding in the Sirenia Stakes, and Nicky confirmed this morning that he was fine with Billy taking the ride." The field is expected to be strong. Leading the pack is George Scott’s dominant Coronation Cup winner Bay City Roller, who is being aimed at the Prix de l'Arc de Triomphe later in the season.

Saeed bin Suroor has entered the Group One‑winning Tornado Alert, with Oisin Murphy slated to ride, while the ever‑reliable Dubai Future will also feature. Among the fourteen possible contenders for the mile‑and‑a‑half contest is last year’s Great Voltigeur Stakes victor Pride Of Arras, representing trainer Ralph Beckett, as well as Owen Burrows‑trained Gethin and Joseph O'Brien’s Small Fry, both regarded as smart performers. Gethin has been a disappointment since his last appearance in the Coral‑Eclipse at Sandown in early July, but Burrows remains optimistic that the horse will rediscover his form at Kempton, potentially using the race as a stepping‑stone toward an Arc campaign.

Callum Rodriguez, who has guided the Wathnan Racing‑owned grey to each of his three career wins, is set to resume his partnership with Constitution Hill. James Doyle is likely to be called upon for the Wathnan team in the Sprint Cup at Haydock later that afternoon. Burrows told Sky Sports Racing: "He's in good shape. Callum had a sit on him last Wednesday because we thought James would be up at Haydock for the Sprint Cup and he was very happy with him.

It's been a bit frustrating we've had to sit on him during the hot months, but we knew we had no issues worrying about weather for this race and I'm looking forward to getting him back out. He was fine after the Eclipse. If you look at the sectionals it was pretty hard for the first four furlongs and quickish ground as well, hence why we didn't want to go again on it." When asked about the prospect of taking on Constitution Hill, Burrows added: "He obviously brings a nice dimension to the race and I'm sure it will add plenty on the gate, but like any trainer I just want to beat all the opposition, so if he's in it then he's included in that.

It will be interesting, but I'm hopeful. Wathnan bought him with an Arc in mind, so if Saturday went well I dare say that will be his next step." The September Stakes will be a true litmus test for Constitution Hill’s transition from hurdling to flat racing.

While his two wins on the flat have demonstrated raw talent and adaptability, the step up to a Group Three over twelve furlongs against seasoned middle‑distance performers will reveal whether he possesses the stamina and tactical versatility required at the highest level. A strong performance could cement his status as a genuine dual‑code star and justify the lofty plans his connections have for an eventual Arc bid. Fans will also be watching how Billy Loughnane handles the pressure of riding a high‑profile horse for the first time in such a competitive environment.

Loughnane has shown promise in his recent rides, notably in the Sirenia Stakes, but the September Stakes will be a far bigger platform. His partnership with Henderson’s stable could prove pivotal, offering the young jockey a chance to showcase his skill on a big stage and potentially earn more top‑class rides in the future.

Overall, the race promises a compelling mix of seasoned Group winners, emerging talent, and a horse making a bold transition. Whether Constitution Hill can rise to the occasion and continue his meteoric rise, or whether the step up proves too much, will be decided on Saturday at Kempton.

The outcome will shape the narrative for the rest of the season, influencing decisions about future targets, including the coveted Arc de Triomphe, and will provide a clear indication of where this former hurdling superstar truly belongs in the flat racing hierarchy.