Police have urged laptop owners to protect their property - saying a thief can steal a computer within seconds.
Det Sgt John Linsdell of Thames Valley Police demonstrated to the Oxford Mail that it takes just 30 seconds to reach through a small gap in an open window and grab a laptop.
Computer theft in the city doubled between 2004 and 2006 because doors and windows are left unlocked.
Det Sgt Linsdell added: "A gap of just 3cm is sufficient for a computer to be stolen."
Although break-ins have fallen by 37 per cent this year, laptop burglary, mainly in student and multi-occupancy homes, and at weekends, is growing - up from 214 in 2004 to 404 last year.
Three were taken from one house in Divinity Road, East Oxford, on Monday night.
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