Cressida Bonas paid an emotional tribute to her "darling sister" Pandora Cooper-Key at a memorial service on Friday.
"My heart is forever tied to yours," the actress, 35, said of Pandora, a ceramicist who died in July aged 51 following a 24-year cancer battle.
Bonas, a former girlfriend of Prince Harry, was joined at St Luke's church in Chelsea, west London, by Pandora's friends including Queen Camilla's son, Tom Parker Bowles.
Wearing a pastel-coloured trouser suit, Bonas read a moving "letter to Pandora" that she composed after her death.
Harry's ex-girlfriend shares heartfelt statement to her 'darling sister'GettyTheir mother, Lady Mary-Gaye Curzon, also paid tribute, saying: "Nobody on Earth who ever met Pandora could help falling in love with her."
Pandora, who was a mother of two teenage boys, said her family had already planned her funeral "thousands of times" just months before her death in an interview with The Mail.
Other family members at the service included Pandora's half-sister Isabella Calthorpe, who was joined by her sister-in-law Holly Branson, daughter of Virgin tycoon Sir Richard Branson.
Actress Gabriella Wilde was in attendance, whose father, John Anstruther-Gough-Calthorpe, is an ex-husband of Pandora's mother, Lady Mary-Gaye.
One of Pandora's friends, Serena Cook, amused the congregation with tales from their travels through Latin America.
She said: "Pandora's creativity [was] always present as she redecorated backpacker hostels entirely with her distinctive style."
Cook added: "We stole watermelons from a field in Nicaragua, scrambling up a tree in absolute hysterics.
"We got chased by a furious farmer."
Cressida Bonas attending Prince Harry's wedding to Meghan Markle in 2018PALATEST ROYAL NEWS:
Cressida Bonas at Princess Eugenie's Anti-Slavery Collective winter gala last yearGettyThe daughter of former It girl Lady Mary-Gaye Curzon and aristocrat Esmond Cooper-Key, Pandora was first diagnosed with Paget's disease, a rare cancer of the milk duct, aged just 26.
She was told that she had an inoperable brain tumour at the end of last year.
The artist endured repeated rounds of immunotherapy in the hope she would recover but was told this was not an option after her latest news.
A notice in The Times, announcing her death, called her a "beloved daughter, adored mother, much-loved sister and devoted aunt". She passed away on July 22.