Queen, Charles send Kate Middleton sweet 40th birthday messages, share new photos

They wrote: “Wishing the Duchess of Cambridge a very happy 40th birthday today!”

The Queen is expected to throw the bash, with Windsor Castle or Sandringham among the likely venues.

Similar lavish bashes have previously been thrown to jointly celebrate significant birthdays of several members of the family at the same time.

Back in June 2000 a huge do was held at Windsor to celebrate Prince Andrew’s 40th birthday, Princess Anne’s 50th, Princess Margaret’s 70th and William’s 18th.

A source told the Mirror: “It’s very much a scaled-down occasion this year for the Duchess, who will celebrate privately with her family.

“Of course she is mindful of the current situation. She will be surrounded by loved-ones and that’s all that matters.”

Kate’s official 40th birthday portraits, taken by Paolo Roversi, are part of the National Portrait Gallery’s Coming Home exhibition. They will go on display in Berkshire, where Kate grew up, St Andrews, where she met Prince William, and Anglesey, their first marital home