Kate Middleton is officially on maternity leave.

The next time we see her, she will have had baby number three and our favourite two royals (AKA Prince George and Princess Charlotte) will have an adorable little sister or brother (we don’t yet know which).

In her last public outing today, the 36-year-old Duchess of Cambridge kept to a tight schedule alongside her husband, Prince William, 35.

She attended a Team SportsAid event at a London Arena, where William joined in playing wheelchair basketball and she was challenged to a Commonwealth quiz alongside athletes, coaches and supporters, E! News reports.

The pair then moved onto St Luke’s Community Centre where they were put to work cooking and preparing for the Commonwealth Big Lunch – a project that encourages the city’s citizens to come together.

Chatting to school students outside the arena, Kate made nine-year-old Given Mkandwire's day when she answered his question about her favourite books to read.

According to People, the boy was too overcome to remember her response but said she told him, "Harry Potter didn't exist when I was little".

"It was amazing to see them," the little fan added.

Kate is due to give birth in April. Her final public engagement comes at the same time invitations to the upcoming wedding between her brother-in-law Prince Harry and his fiance Meghan Markle are being sent out.

Check out the beautiful invites here.

LISTEN: Meghan Markle had to go to 'kidnap training'.