Kate Middleton, who is expecting her first baby in July, looked obviously pregnant for the first time as she attended the National Review of the Queen’s Scouts at Windsor Castle.

The Duchess of Cambridge, 31, was replacing Queen Elizabeth II at the event as the monarch is celebrating her 87th birthday privately.

A volunteer in the Scout Association, Kate Middleton, 31, has worn an extremely short pastel Mulberry coat, fawn pill box hat and her favorite nude LK Bennett heels.

Kate Middleton has worn her Whiteley Cappuccino hat on several previous occasions, including the Epsom Derby.

The event is a day of celebration, bringing together 400 Queen’s Scouts and their invited guests to celebrate the achievements of young people and young adults who have achieved the prestigious award.

It is gained by carrying out regular community service for a year, learning new skills, completing a four day expedition in unknown terrain; taking part in a residential project and then sharing what has been learned with their peers.

Kate Middleton, who is expecting her first baby in July, looked obviously pregnant for the first time as she attended the National Review of the Queen’s Scouts at Windsor Castle

During the event, Kate Middleton spent time talking with some of the 400-plus Queen’s Scouts from around the UK and the Commonwealth.

She also met gallantry award holders, who have been nominated for their bravery and heroism and meeting adversity in their everyday lives.

The tradition of the annual celebration event within Windsor Castle dates back 80 years.

Since its inception, tens of thousands of young men and women have been honored with a King’s or Queen’s Scout Award for their own outstanding personal achievements.

Today, The Scout Association hailed the Duchess of Cambridge, who volunteers occasionally with a Cub Scout group close to her home in North Wales, for a sharp increase in the number of adult volunteers.

A spokesman for the Scouts said the Duchess had done around half a dozen volunteering sessions with her local cubs this year.

Kate Middleton is one of 2,812 new adult volunteers to join this year. These figures represent the second biggest increase in adult volunteers since 1986.

As well as attracting more adults the total number of teenagers in Scouting has almost doubled in the last 10 years, from 23,446 in 2003 to 40,578 in 2013.

However, despite attracting more adults, the Movement still has 37,867 young people on waiting lists who are unable join up because even more adult volunteers are needed.

Bear Grylls, Chief Scout, said: “It’s great that so many adults are joining the Scouts, and I am sure the increase has had much to do with the Duchess of Cambridge becoming a Scout volunteer last year.

“The Duchess is an incredible role model and she helps us show that Scouting’s not just for boys.

“She’s also such a generous volunteer and everyone is so excited to have her in the Scouting family. Many people have followed her lead and are getting involved and enjoying the adventure.”