Big Buck's will be searching for a 14th victory in a row as he competes in the Long Walk Hurdle at Ascot on Saturday.
The horse, trained by Paul Nicholls, has not lost since unseating rider Sam Thomas in the 2008 Hennesy Gold Cup.
Nicholls soon switched Big Buck's to hurdles and 3 Cheltenham World Hurdles have vindicated his decision.
Victory at Ascot would see the eight-year-old go past the £1m mark in career earnings and beat Champion Hurdler Bula's winning run of the 1960's.
Big Buck's biggest challenger in the Long Walk Hurdle may be stable mate Five Dream, who finished second behind him in the Long Distance Hurdle at Newbury last month.
