Kate and William's first joint public appearance since his cancer treatment CNN

Britain's Prince and Princess of Wales made a surprise visit to Southport in northwest England on Thursday, where they met the grieving families of three children killed in a knife attack in July.

The visit was the first public appearance of Catherine, known as Kate, since she completed her chemotherapy treatment.

Bebe King, 6, Elsie Dot Stancomb, 7, and Alice da Silva Aguirre, 9, were fatally stabbed on July 29 while attending a Taylor Swift-themed dance class in the city.

The royal couple met privately with the families of the three young women and their dance teacher who was present during the attack.

William and Kate – who have made only a handful of public appearances this year – also met emergency service workers who responded to the scene in July, as well as mental health practitioners who have been supporting the “blue light” community for months.

“I can't underestimate how grateful they are [the families] It's all about the support you gave that day, Kate told respondents during a deeply emotional sit-down, according to Britain's PA media news agency. He then thanked the frontline workers on behalf of the family.

Meanwhile, William, the heir to the British throne, told the group they were “brave” and urged them to “make sure you take care of yourself”.

“Please take your time, don't rush back to work,” he added.

After the surprise appearance in Southport, William and Kate spoke of their “powerful” visit on social media.

“We stand with everyone in Southport. Meeting the community today has been a powerful reminder of the importance of supporting one another in the wake of unimaginable tragedy. You will be in our thoughts and prayers,” the couple wrote in a post on X.

At the time of the knife attack, Wells released a statement on social media from their parents' perspective. “We cannot begin to imagine what the families, friends and loved ones of those killed and injured in Southport are going through today,” they said in July, before sending their “love, thoughts and prayers” and gratitude to emergency responders.

The couple made a donation to raise funds through their royal foundation, which has been set up to provide mental and physical rehabilitation for police and ambulance workers involved in the attack and subsequent riots.

CNN understands that the princess decided to join her husband on Thursday to show her support, sympathy and compassion for the local community.

Kate, 42, eased her way back into public life after announcing in a video last month that she had completed chemotherapy and was declared cancer-free. He did not disclose what type of cancer he was being treated for.

The princess said the past nine months had been challenging but “however, I'm looking forward to getting back to work and doing some more public engagements in the coming months when I can.”

In recent weeks, he has been holding several meetings focused primarily on his first year of work and his upcoming annual Christmas carol concert.

He made a private visit to English National Ballet for a matinee show a few weeks ago, later posting on social media about the “moving and inspiring” performance.

Wales is not the only member of the royal family to show their support for the grieving family and the Southampton community. King Charles III made a similar visit to the region in August to meet victims of the attack and thank frontline emergency workers.

This story has been updated.