unfortunately an alarm only deters the oppotunist thief, the professional theif will have your bike in the back of a van in under 10secs, the van will be sound proofed and anyway no one batts an eyelid at a alarm going off these days, your best bet is to chain the bike to something and have an alarm aswell. but its almost impossible to find something to chain a bike to in central london, push bikes are better off than motorbikes
if your out with a friend, chain two bikes together.
i'd love to catch one of em, although i'd be getting done for murder
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