Prince William joined Sophie for a rare joint engagement on Tuesday evening.
The Duchess of Edinburgh, 58, and Prince of Wales, 40, attended the screening of Rhino Man at Battersea Power Station.
The pair arrived at the engagement in a black four-by-four.
Sophie was spotted beaming as the mother-of-two got out of the vehicle alongside the Prince of Wales.
Sophie (left) and Prince William (right)
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The Duchess, who was returning to royal duties following the tragic death of an 81-year-old woman who was hit by her police motorcycle escort last month, wore a sleeveless frock and nude strappy sandals.
She was also clutching onto a dark purple bag which matched her outfit.
The Prince of Wales meanwhile donned a navy suit with a matching dotted tie and black shoes.
Rhino Man, which was produced by the charity Global Conservation Corps, was screened in South West London.
Prince William and Sophie, Duchess of Edinburgh, attend a United for Wildlife screening of documentary Rhino Man
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The documentary uncovers the life of field rangers in South Africa.
It shows how they risk their lives on a daily basis protecting rhinos from poachers in a bid to prevent their extinction.
Anton Mzimba, a South African ranger who was murdered by wildlife traffickers in July 2022, features throughout the film.
Prince William connected with Mzimba months before his death.
The Duchess of Edinburgh attends the Not Forgotten Association Annual Garden Party at Buckingham Palace
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The father-of-three met with his sister ahead of watching the film.
Prince William said at the event: “The murder of Anton Mzimba is a stark reminder of the daily dangers that all rangers face around the world protecting the natural world from the international criminal organizations that seek to profit illegally from wildlife, and I’m proud to see his life and legacy recognized in Rhino Man."
"This is not a burden they can bear alone.
"An effective response to this vicious crime demands attention and collaboration across the entire chain of criminal activity, not just on the front line.
The Prince of Wales (left) attends a private screening of Rhino Man, hosted by United for Wildlife at The Cinema at Battersea Power Station in London
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“That is why United for Wildlife, through its global financial and transport task forces, and wider alliance of partners, has taken action to ensure that those involved in wildlife crime will be met with an international response as powerful and coordinated as any other serious and organized crime."
However, the Waleses and Edinburghs have been making more public appearances with each other in recent months.
The quartet sat together in the front row of Westminster Abbey for King Charles’s Coronation last month.
They would later lead Buckingham Palace’s garden party two days later.