The Irish Guards' regimental mascot, Conmeal the Irish wolfhound, was given his own sprig of shamrock by the Duchess of Cambridge.
The St Patrick's Day tradition dates back to 1901.
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Masood's body was identified using DNA and fingerprints.
Medical staff who helped during the Westminster terror attack have received a royal thanks for their life-saving efforts.
Temperatures reached 21.8C in Gravesend making it the hottest day of 2017 so far.