Three men were chased by a police officer after a bungled break-in at a South Oxhey school.
The gang was seen jumping over the gate of St Joseph's Catholic Primary School by a PC who was on patrol.
After failing to get in through windows and doors of the Ainsdale Road school, the trio ran off at 11.45pm on Tuesday.
A 20-year-old from Watford has been arrested and in custody.
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