She accessorised the look with a pair of brown Stuart Weitzman ankle boots and a pair of chic sunglasses.
While Pippa was sure to have caught the attention of onlookers, it was baby Arthur who stole the show.
Sightings of the tot have been few and far between, so fans were thrilled to get a glimpse of Arthur looking out from his pram during the day out.
The baby was rugged up against the London weather in a sweet pale blue outfit and appeared to be in good spirits.
While we are sure that Arthur has plenty of playdates with his cousins, Prince George, Princess Charlotte and Prince Louis, the bub is set to have a new playmate at the palace as Meghan Markle is set to give birth any day.
Watch the video to find out about Meghan and Harry's baby.