William reveals he was '˜very angry' when his mother Diana died in a car crash

William’s candid comment came at the start of a year that will see the 20th anniversary of Diana’s death marked over the coming months.

He spoke openly during a visit to an east London bereavement centre with Kate where they sat down with families making memory jars in honour of a loved one who has died.

As Lorna Ireland, 36, and her son Shinobi Irons, 12, each filled their individual jars with bands of coloured salt - representing memories of the youngster’s grandmother who died three years ago and godmother who died in 2015 - the future king spoke about his feelings.

Miss Ireland said: “He told my son that when his mum died he was 15 at the time and he was very angry and found it very difficult to talk about it.

“So it was very important that Shinobi talked to somebody about how he was feeling even now years on.”

She said about the admission: “It was very personal and it was very special.”

The Duke was a teenager and his brother Prince Harry was just 12 when their mother Diana was killed in a car crash in Paris on August 31 1997.

In recent years the royal siblings have begun to talk about their feelings surrounding their loss with Harry saying last summer in an interview he now regrets not opening up sooner about how his mother’s death affected him.

William and Kate were visiting a bereavement centre in Stratford run by Child Bereavement UK which the Duke supports as royal patron.

The organisation, first launched in 1994, had Diana as a keen supporter and today it continues to support parents who have lost children as well as offering help to a child if they experience bereavement themselves.

Ann Chalmers, chief executive of Child Bereavement UK, acknowledged that William’s own experiences allowed him to understand what grieving families were going through.

She said: “The Duke of Cambridge has been our royal patron since 2009 and it’s really important for him to see our work at close quarters and the most important thing for him is to meet the families that we support.”

The chief executive added: “I think one of the things that’s really apparent when you hear the Duke talking to the families is that he has a real empathy and depth of understanding of their situations.

“He’s also a fantastic listener and really wants to learn from the families what the challenges are that they’re facing, and in that there are some things he can recognise from his own experiences.”

Before leaving William and Kate cut a cake to mark the first anniversary of the Stratford bereavement centre, and the royal couple both held the knife as they performed the ceremony.