Kate Middleton's birthday heartache over Prince William's 'crushing' decision

Kate Middleton once faced birthday heartache after Prince William made 'crushing' decision to go away after her big day.

• Kate Middleton was reportedly left 'crushed' after Prince William announced he was joining the RAF shortly after she turned 27.
• The Duchess of Cambridge had just celebrated her birthday when the Duke dropped the bombshell plan.
• This royal news comes as the ‘triggering’ thing people do to Kate Middleton that Prince William WON’T tolerate was revealed.

Kate Middleton was once left heartbroken after Prince William made a 'crushing' decision to join the RAF.

The move meant that William had a three-hour drive from London to Shropshire, at a time when he and Kate were getting serious and she was forced to say an emotional goodbye to her future husband, in a decision that made her 'crushed' after her 27th birthday.

And as Kate prepares to mark a low-key 40th, it's expected to be spent surrounded by her family.

While her 27th is possibly one she'd like to forget, as it's claimed Kate had been expecting William to propose but instead, he announced that he was to join the RAF in 2008 - a decision that surprised both his family and his girlfriend.

At the time Prince William had just completed assignments with each section of the Armed Forces and he was left with two choices - either to return to the Household Cavalry or quit and begin his royal duties.

But for the young prince, the RAF career path allowed him extra time and freedom before starting his royal journey full time - an independent life that both his father, Prince Charles, and his grandmother, the Queen, were denied.

And aircraft is a passion which his children now share.

Royal author, Katie Nicholl, writes in her book Kate: The Future Queen, "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."

Kate Middleton's birthday heartache led to 18 months of training in Shropshire followed by two years at a remote location in the UK.

The monarchy pro adds, "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."

With their relationship set to be put to the long-distance test, the couple enjoyed a holiday in Scotland before his RAF life kicked off.

"For Kate, it was a step backward. 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."

But following Kate Middleton's birthday heartache William did propose in 2010 and the couple, who now have three children, Prince George, eight, Princess Charlotte, six, and Prince Louis, three, celebrated their 10th wedding anniversary last year.

No doubt Kate will be treasuring every minute of her birthday this year after her mum Carole hinted at celebrating in the birthday month with her family as she turns 66.