They toured Kensington Palace's sunken garden which had been transformed into a memorial space planted with white foliage and flowers in honour of Diana.
Victoria Murphy, a journalist on the scene, tweeted that one of Middleton's aides informed her that the Buchess of Cambridge's "condition is improving but she is still suffering from hyperemesis gravidarum". "She's delighted to be here tonight".
The duke and duchess and Prince Harry arrived via a well-known hidden door in the Palace's white drawing room and waiting to meet them were leading figures from the mental health sector including Mind president and comic Stephen Fry.
But in the most surprising twist to date, sources tellNew Idea that the duchess is already five months along - two months more than what was previously believed - meaning that we will meet their double-bundle of joy early in the New Year.
"It was Catherine who first realized that all three of us were working on mental health in our individual areas of focus. She had seen that at the core of adult issues like addiction and family breakdown, unresolved childhood mental health issues were often part of the problem".