The WHSmith's Pinner branch was broken into in a burglary which set off the shop alarm and alerted the police.
Metropolitan Police officers arrived in Bridge Street at around 12.30am on Friday (January 6) after reports of the alarm was raised.
A spokesman for the force told getwestlondon: "We were called to the scene to reports of a non-residential burglary because of the alarm reactors."
Upon arrival, Harrow police noticed the gates "had been rammed open", showing forced entry into the store.
Photographs taken by inspectors show the destroyed interior of the store, with paper, pens and other stationary across the floor after the break in.
Enquiries still continue as inspectors look into what was taken from the property.
Pinner resident Audrey Lee-Mower said she heard the alarm but didn't think there had been a burglary until police arrived.
The 58-year-old, who lives a short walk from Bridge Street, said: "It's not a quiet road, so it's quite unexpected for it to happen.
"The store is popular and it's not nice seeing it in that state. Let's hope those responsible are caught."
WHSmith has been approached for comment.
Anyone with information should call police on 101 using the incident reference "222/6Jan17".
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