The 450 soldiers of the 1st Battalion of the Irish Guards prepared to welcome the Duchess of Cambridge.
She will present the sprigs of shamrock to Officers to celebrate St Patrick's Day. Conmael, the Irish Wolf Hound regimental mascot will also receive his own sprig.
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The memorial service will be attended by Prince Harry and Meghan Markle.
David Browning admits manslaughter by diminished responsibility but denies murder.
Four people have died and the suspect is still at large, police said.