Princess Kate’s children – Prince George, Princess Charlotte and Prince Louis – together with her husband Prince William, consistently pull out all the stops to ensure her birthday is memorable.

Throughout the years, she has experienced noteworthy celebrations, ranging from nights out on the dance floor with her sister Pippa to cosy family get-togethers with the Middletons. Yet, her 27th birthday probably remains etched in her memory for rather unfortunate circumstances, as she faced an emotional parting from Wills due to a decision that left her “crushed”.

By that point, the couple had been romantically involved for several years, initially crossing paths at St Andrew’s University when they were 19, though Cathrine’s aspirations for a Royal proposal had yet to materialise.

In September 2008, precisely when rumours intensified that the Duke was about to pop the question, it was officially announced that he would be enlisting with the RAF – a development that took both his relatives and partner by surprise.

Having just completed attachments with various sections of the Armed Forces, William was presented with two paths – return to the Household Cavalry or withdraw from military duties to begin his Royal obligations.

For William, opting for an RAF posting granted him extra time and autonomy before completely taking on his Royal position, affording him a degree of personal liberty that neither his grandmother nor father had enjoyed. However, for Catherine, it signified a disappointment as numerous observers had expected her to wed the prince and begin her Royal path, reports the Mirror.

In her publication, Kate: The Future Queen, Royal commentator Katie Nicholl chronicles: “With that single decision, Kate’s life was turned upside down. She had expected a proposal once William had completed his military training, but instead, she was forced to accept that there would be no engagement any time soon. Kate would have to wait even longer.”

The Prince’s fresh assignment demanded 18 months of preparation in Shropshire, succeeded by a two-year deployment at an isolated British base. Katie documents: “Was Kate prepared to join him? She supported his desires and ambitions, but privately she was crushed. William was asking her to be an army wife – without the nuptials. Her frustration was understandable.”

During the subsequent weeks, the couple savoured quality moments in Scotland, marking New Year together, whilst Kate also embarked on a family getaway. Yet, as her birthday approached, the Prince needed to embark upon his career’s next phase.

Katie suggests William remained confident their bond could endure the separation, given the Shropshire station sat approximately three hours from London.

Katie maintains that Catherine found the situation increasingly difficult as their social circle began establishing families whilst she existed in uncertainty. She writes: “For Kate, it was a step backwards. It seemed that everyone was getting married except for her. As she neared her 27th birthday, Kate’s plan to be married with children by the time she was thirty was looking increasingly unlikely.”

Katie indicates that it wasn’t just Catherine who was feeling nervous – her mother, Carole Middleton, was also growing “jittery”.

Despite the hurdles, the couple managed to keep their relationship strong, with William often making the 130-mile trip back to Bucklebury to see Catherine. By the close of 2010, William finally formalised things by proposing.

The couple decided to keep their engagement under wraps at first, before publicly declaring it on 20 November. They tied the knot in a grand Royal ceremony at Westminster Abbey in April 2011.