Duchess Catherine would need to be ''superhuman not to feel the pressure'' of her role.

The 38-year-old royal - who has Prince George, six, Princess Charlotte, five, and Prince Louis, two, with Prince William - is a strong character but faces mounting public expectation, according to royal expert Sarah Gristwood.

The author of 'Elizabeth: The Queen and the Crown' told PEOPLE magazine: ''Those who know her say there is a real core of strength, and she did set her mind to the job.

''But at the same time, she'd have to be superhuman not to feel the pressure.''

The decision of Prince Harry to step down as a senior member of the royal family has pushed the Duchess - who married Prince William in 2011 - into the spotlight even more than before.

A source explained: ''Without Meghan and Harry, there is going to be a phenomenal workload on Catherine and William.

''None of the older [generations] can do it all. The pressure is on the two of them.''

Meanwhile, royal expert Myka Meier, author of 'Modern Etiquette Made Easy', thinks the Duchess is already very conscious of the image she presents of herself.

Myka said: ''The future Queen is a role model to the UK but also to the world, which means all eyes are on you.

''The added pressure of having cameras everywhere to catch even the slightest eye movement makes everything she does a conscious effort. From the perfectly poised posture to the way she descends a staircase or gets out of a car - it is all carefully done.''

The Duchess is also said to have derived confidence from her royal work.

A source explained: ''Catherine is the sort of woman who will take on whatever she needs to. If she needs to step up to the plate, she does it - and she always has.''