Kate and her husband Prince William were guests at the ceremony, which took place at Chelsea Old Church - situated on the same road where the Duchess previously lived at the former Middleton family home in west London.

The mother-to-be looked elegant in a floor-length black lace gown, as she wrapped up warm with a red tartan scarf, hiding her blossoming baby bump. 

Kate's frock looked to be the same as the dress she wore to attend the star-studded Royal Variety Performance last month. 

Smartly-dressed William kept close to his wife, who is five-months pregnant with their second chid,  as she led the way in front.

The Duchess accessorised her long-sleeved dress with a simple black clutch bag and her brunette tousled locks down below her shoulders.  

Mysteriously, Kate's engagement ring was turned inwards only to show her band. 

The royal couple, both 32, were flanked by seven Metropolitan police officers as they made their way to a waiting car. 

It was a weekend off from royal duties for Kate and William, who returned home after taking New York by storm during a three-day milestone visit last week.