The Lindo Wing at St Mary's Hospital where the Duchess of Cambridge will give birth to the royal baby in a few weeks has undergone an 18 month refurbishment.
Acclaimed visual artist, London born Julian Opie is providing 40 panels to be displayed over the units four floors.
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David Cameron said the Met proved it can "do more with less" and declined to criticise the Mayor of London for his water cannon spend.
A group of disabled activists threw toys and balls at him as he entered the conference.
A wet start to the week and the unsettled weather is set to continue over the next few days.