Ms Nicholl said: “There are two roles to a future Queen.
“One is to produce heirs, which she has done and one is to learn one day to become Queen.
“That is very much what we are seeing, we are seeing a Queen in waiting.
“We are seeing the Duchess take on more duties, more royal engagements, more of a public profile than ever before.
“She is taking on patronages from the Queen and the Duke of Edinburgh.”
Kate, 39, has three children with Prince William, 39, who is second in line to the throne.
Firstborn Prince George was born in 2013, followed by Princess Charlotte in 2015 and Prince Louis in 2018.
Kate and Prince William were spotted at the premiere of the new James Bond Film, “No Time to Die”, earlier this week.
Kate turned heads in a shimmering gold gown alongside Prince William, who looked suave in a tuxedo-style jacket.
In recent weeks, the Duchess of Cambridge has attended a number of high-profile royal engagements up and down the country.
She travelled to Lake Windermere to abseil and go mountain biking while meeting young air cadets, and visited RAF Brize Norton to talk with military personnel involved in the evacuation of civilians from Afghanistan.
Source: EXPRESS CO UK