Prince William and Kate are celebrating their 13th wedding anniversary.

The Princess of Wales, who is undergoing chemotherapy for an undisclosed cancer, married future king William in 2011 after eight years of dating.

The pair are facing their most difficult challenge so far amid the princess’s diagnosis, with Kate appealing for time, space and privacy as she continues her treatment.

She praised her husband for his support during “an incredibly tough couple of months for our entire family” in an emotional message to the nation in March announcing her health news.

“Having William by my side is a great source of comfort and reassurance,” she said.

Kate, 42, told how her diagnosis had come as a huge shock and that she and William “have been doing everything we can to process and manage this privately for the sake of our young family”.

The prince returned to work after the Easter holidays when the duke and duchess spent quality time with their three children Prince George, Princess Charlotte and Prince Louis.

Louis celebrated his sixth birthday on Tuesday and Charlotte turns nine on May 2.

Partners for more than 20 years, William and Kate met at the University of St Andrews in Fife, Scotland, and became friends first before embarking on a romance.

They wed in a grand fairytale ceremony in Westminster Abbey on April 29, 2011, with the aisle of the gothic church lined with trees.

William and Kate welcomed their first child George in 2013, followed by Charlotte in 2015 and Louis in 2018.

They have shared ups and downs, from the arrival of their children and the celebration of Jubilees to the late Queen’s death and more recently the King’s cancer diagnosis.

The couple also weathered accusations levelled at them by William’s brother Harry and his wife Meghan after their split from the royal family.

Thirteen is superstitiously considered an unlucky number but is also known as a baker’s dozen, which dates from medieval times when vendors would add an extra loaf to avoid being flogged for overcharging customers for their regulated goods.

Thirteenth wedding anniversaries are traditionally marked with the gift of lace.