The sister of Cressida Bonas, who once dated Prince Harry, has passed away after years in poor health.

Pandora Cooper-Key, half-sister of Cressida Bonas, has died aged 51 after suffering with different types of cancer for over two decades.

Cressida was in a relationship with Prince Harry from 2012 until 2014, before he met Meghan Markle, and although things did not work out they remained on good terms.

Pandora was first diagnosed with cancer 24 years ago, when she was just 26, and revealed in March this year that she had already been planning her funeral after she was found to have an inoperable brain tumour.

She was the daughter of Lady Mary-Gaye Curzon and aristocrat Esmond Cooper-Key, and is survived by her 77-year-old mother, although her father died in 1985.

At the end of last year a tumour was discovered on the left side of Pandora’s skull, leading to her having immunotherapy even though it could not be surgically removed.

Pandora Cooper Key has died (Image: Getty)

Pandora’s battle with cancer began in 2000 when she was diagnosed with Paget’s disease, a rare cancer of the milk duct, with her later having a sarcoma in her left eye and sinus area.

After an operation to remove her tear duct, Pandora later had tumours in her cheek and eye removed before suffering a series of seizures in 2016 that sometimes left her unconscious for a week at a time.

Despite this Pandora continued to fight back against the disease, telling Femail earlier this year about her brain tumour: “[To operate] they’d have to go through blood vessels and that’s not great.

“So they categorically said in the first meeting ‘I’m really sorry, but we can’t.’

Cressida and Harry dated for two years (Image: Getty)

She added: “In the last few months, I probably have been the closest to feeling depressed than I’ve ever been and I’m not a depressive person.

“That’s been quite scary. There have been days where I’ve been like I can’t bear the pain. But then there’s something in me that bounces back.”

A notice in The Times today (August 3) called Pandora a “beloved daughter”, “adored mother”, “much-loved sister” and “devoted aunt

Pandora has been open about her health battles (Image: Getty)

Sarcoma UK, a charity she supported, said on a fundraising page: “She was a beautiful spirit and an inspiration to so many.”

Kerry Reeves-Kneip, Director of Communications at Sarcoma UK, added: “Her openness about her journey helped raise crucial awareness about sarcoma and the challenges faced by patients. Pandora’s legacy extends far beyond her fundraising efforts; she touched countless lives with her warmth and resilience.

“On behalf of everyone at Sarcoma UK, I extend our deepest condolences to Pandora’s family, including her mother, Lady Mary, her sister, Cressida Bonas, her two sons, and all who loved her.

“We are immensely grateful for the difference Pandora made to our organisation and to others affected by sarcoma. We at Sarcoma UK will honour her by continuing our mission with renewed determination. Pandora’s kindness, courage, and indomitable spirit will forever remain in our hearts.”