After the service, conducted by the rector of Sandringham Jonathan Riviere, the Prince of Wales and Duchess of Cornwall chatted to Park House residents while the Queen was presented with gifts from children.
The Queen was wearing a burnt orange cashmere Stewart Parvin coat, fur hat and a diamond brooch.
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Sergeant Elor Azaria was caught on video shooting dead the wounded assailant, sparking one of the most divisive cases in Israel's history.
CAFOD said: "Hunger is evident in the thinness of children, and the way clothes hang from the bodies of people already suffering."
Police believe it is a "distinct possibility" that Halliwell was a serial killer, beyond the two murders he was convicted for.