Her chronic antenatal sickness has meant she has not been seen in public for more than seven weeks.

But last night the Duchess of Cambridge, at 13 weeks pregnant, proved she still has the power to dazzle.

Showing off plenty of leg – but not yet any hint of a bump – Kate pulled out all the stops in a floor-length powder blue evening gown by Jenny Packham at a glamorous black tie event at London’s Natural History Museum.

She looked as stylish as ever – if a touch on the peaky side – as she undertook her first official engagement since early August, dressed in a made-to-measure check Alexander McQueen coat that hid any hint of her blossoming pregnancy.

In her grey Jane Taylor hat and her vertiginous black Prada heels – completed with £1,090 Annoushka pearl earrings – she and William towered over the diminutive president Tony Tan Keng Yam and his wife Mary.

Kate admitted she was ‘delighted to be out of the house’ after being laid low for weeks by hyperemesis gravidarum, the chronic antenatal sickness that saw her hospitalised while she was expecting her now 15-month-old son, Prince George.

According to sources, Kate has been ‘terribly ill’ and at one point retreated to her parents’ home in Berkshire to recuperate.