Fiennes, 63, is also attached as an executive producer on the project, which will tell the story of Cecil’s personal and professional struggles before his extraordinary return to the top with Frankel.

Frankel retired unbeaten after winning all 14 of his races, including 10 at Group 1 level – between 2010 and 2012.

His performances captivated racing fans around the world, while his partnership with Cecil became one of the sport’s most celebrated stories of resilience, trust and sporting excellence.

The project will be directed by German filmmaker Nora Fingscheidt, with a screenplay written by Bash Doran.

Tony Rushmer, author of The Triumph of Henry Cecil: The Authorised Biography, is serving as a consultant to help bring authenticity to the portrayal of the legendary trainer and his career.

Fiennes said he was moved by the screenplay and Cecil’s story. Describing the trainer as a unique and complex figure in the highly competitive world of horse racing.

The film is being developed by House Productions, Escapade Pictures and Studiocanal, with support from BBC Film and Access Entertainment.

When is the Frankel biopic expected to be released, and on which channel?

An official cinema release date has not yet been announced.

Unlike a television documentary, Unbeaten is being developed as a feature film for theatrical release.

Studiocanal will handle its cinema distribution in the UK and several international territories, as well as worldwide sales.

BBC Film has supported the project’s development, but no television broadcast date or confirmed TV channel has been announced.

BBC Film’s involvement should not be taken as confirmation that the movie will premiere on BBC television.

The story is expected to focus on Cecil’s later years, his personal difficulties.

Plus his relationship with Jane Cecil, before following his partnership with Frankel and the remarkable success that transformed his final years in racing.

Sir Henry Cecil’s extraordinary training career

Sir Henry Cecil was one of British horse racing’s most successful and admired trainers.

Born in Aberdeen on January 11, 1943, he established his training career in Newmarket. And became a dominant force in Flat racing for more than four decades.

Cecil first took out his own training licence in 1969.

His breakthrough at the highest level came with Bolkonski, who won the 2,000 Guineas in 1975. Followed by Wollow’s victory in the same Classic a year later.

His success continued through the 1980s and 1990s, when his Warren Place stable became synonymous with elite racehorses.

Sir Henry Cecil achievements included:

• 10 champion trainer titles in Britain.

• 25 British Classic victories, including four Epsom Derby winners.

• Four St Leger winners and eight Epsom Oaks winners.

• A remarkable collection of champion horses, including Oh So Sharp, Reference Point, Bosra Sham, Midday and Frankel

Frankel’s Career In Numbers

• Runs: 14

• Wins: 14

• Group One Wins: 10

• Age Retired: 4

• Career Winnings: £2,998,302

WATCH: ALL Frankel’s 14 Career Wins

Cecil was knighted in 2011 for his services to horse racing.

However, his career was not without difficulty. Personal heartbreak, health problems and disputes with major owners contributed to a prolonged downturn in his fortunes, making his late resurgence with Frankel all the more remarkable.

Frankel: the horse that completed Cecil’s legacy

Frankel was Cecil’s crowning achievement. Owned by Prince Khalid Abdullah and ridden throughout his racing career by Tom Queally, the extraordinary colt won all 14 of his starts between 2010 and 2012.

His victories included the 2,000 Guineas, the St James’s Palace Stakes, the Sussex Stakes on two occasions, the Queen Elizabeth II Stakes and the Champion Stakes (watch below).

He retired in October 2012 with an unbeaten record and was widely celebrated as the world’s leading racehorse.

Frankel’s success also gave Cecil a triumphant conclusion to a career that had appeared to be in decline.

The horse’s brilliance and the trainer’s ability to bring him to the peak of his powers form the emotional centre of the new biopic.

When did Sir Henry Cecil die?

Sir Henry Cecil died on June 11, 2013, aged 70, after a long battle with stomach cancer.

He had been diagnosed with the disease in 2006 and continued to train horses while undergoing treatment.

Although his health deteriorated during his final years, he remained involved in racing and witnessed Frankel’s extraordinary rise to international fame.

Frankel’s final victory in the 2012 Champion Stakes at Ascot was particularly poignant.

Cecil was there to celebrate the unbeaten champion in front of the crowd, including Queen Elizabeth II, and famously described Frankel as the best horse he had ever trained or seen.

Cecil died less than eight months later, leaving behind one of the greatest records in British racing. His death prompted tributes from across the sport, with many remembering not only his achievements but also his horsemanship, personality and determination to return to the top.

The forthcoming Unbeaten biopic will revisit that final chapter: the story of a trainer fighting personal adversity and a remarkable racehorse whose flawless career helped cement his place in sporting history.