A pregnant Kate Middleton, the Duchess of Cambridge, leaves hospital following treatment for acute morning sickness.

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The Duchess of Cambridge was discharged from King Edward VII hospital on Thursday morning, having been admitted on Monday with hyperemesis gravidarum.

Kate Middleton outside hospital on Thursday morning (Reuters)

She mouthed that she was "much better" to the shouted enquiries from the assembled media, whilst posing for photographs with her husband Prince William. The couple's office said the duchess would head to Kensington Palace for a period of rest.

The duchess is not yet 12 weeks pregnant, but news of the pregnancy emerged after she was admitted to hospital - following a frenzy of global media attention.

Find out more: What is hyperemesis gravidarum?

Yesterday it was revealed that this attention had lead to staff at the hospital revealing information about Kate's condition to two radio DJs, who telephoned the hospital pretending to by Queen Elizabeth and Prince Charles.

And the prank was on the mind of Prince Charles as he spoke to reporters on Thursday about the prospect of becoming a grandfather for the first time.

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