Kate Middleton snubs Queen Elizabeth's historic invite: Duchess refuses to join major event

Even before Kate Middleton became royalty, she prompted Queen Elizabeth to break royal traditions in her favour. 

One such thing happened when the Queen extended a historical invite to Kate even before she tied the knot with Prince William. 

As revealed in Battle of Brothers, author Robert Lacey writes that the British monarch overlooked royal tradition to invite Kate to a major festive event at the Palace.

However, she turned the invitation down!

This was the Queen's first invitation to an unregistered partner for the family's traditional Christmas lunch in 2006.

But Kate, who was 24 at the time, declined the historic request.

Kate "would go to Sandringham on Christmas Day only when she was engaged and had a ring to prove it," Lacey writes in his explosive book.

"By 2006, the couple had been dating seriously for the best part of five years. Yet when William invited Kate to join him that year at Sandringham for the Royal Family's traditional Christmas lunch, she refused.

"It was the first time the Queen had extended such an invitation to an unregistered 'girlfriend', but Kate had her own take on that break with tradition: she would go to Sandringham on Christmas Day only when she was engaged and had a ring to prove it," he adds.

The book also divulges how William wanted to make sure he is not rushing things with Kate before settling down with her.

"William turned to his father and grandmother for guidance. The Queen had grown very fond of Kate, but she told him he shouldn't rush into a commitment — and his father advised the same. In any case, William was enjoying the life of a hard-drinking Army officer. Not for nothing was his new regiment known as the 'Booze and Royals,'" Lacey reveals.