Boris Johnson has praised the "bravery" of PC Andrew Harper after the police officer was killed attending to a reported burglary in the Berkshire village of Sulhamstead.
Ten males aged between 13 and 30 have been arrested on suspicion of murder and remain in custody at various police stations across the Thames Valley.
The prime minister described PC Harper's death as "a mindless and a brutal crime".
Report by Jonesia.
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