Sheltered from the Welsh rain by an umbrella, Kate discussed the ring with a member of the public, explaining how it is the exact same size as it was when she first tried it on.
In a video uploaded to Instagram by Laura-Ann Barr Kate says that it is a shame she never got to meet Diana and that they miss her every day, adding what a wonderful grandmother she would have made.
Diana has five grandchildren in total, Kate and William’s children Prince George, Princess Charlotte and Prince Louis, and Prince Harry and Meghan Markle’s son Prince Archie and daughter Princess Lilibet.
While in Wales today Kate and William made a poignant visit to the Aberfan Memorial Garden, created to remember the 144 people who died in the disaster.
On the morning of October 21, 1966, 116 children and 28 adults were killed when a landslide of coal fell down a mountainside and crashed into the village, with Pantglas Junior School bearing the brunt of the impact.
The memorial garden stands on the site of the school and was opened in 1974 by the late Queen Elizabeth.
The Waleses met with one of the survivors of the catastrophe and Professor Peter Vaughan, Lord Lieutenant of Glamorgan, who showed them around the garden.
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They were also joined by trustees from the Aberfan Memorial Trust, who are in charge of maintaining the garden, and the Aberfan Wives, relatives of those who died in the tragedy.
On their first day in Wales on Thursday Kate and William enjoyed an action-packed day of abseiling while visiting the Central Beacons Mountain Rescue Team in Merthyr Tydfil.
Sporty Kate appeared to relish the challenge as she was pictured laughing and smiling on the mountainside.
She later joined William to help deliver pizza from the Little Dragon Pizza Van at Dowlais Rugby Club, which they shared with rescue teams in Dowlais.
Peter Morris, owner of the Little Dragon Pizza Van, who served the couple with colleague Shannon Stokes, said it was “surreal” serving the royal couple.
He told People magazine: “The Princess asked if we make our own dough — and said that they love making pizzas with their children.”
Next week the Waleses and their children will have the eyes of the world on them as they attend King Charles and Queen Camilla’s Coronation.
As heir to the throne, William will have to pay homage to his father as part of the ceremony.