YALE Maxi Lock, £29.99, www.yale.co.uk

A slightly different take on the cable lock from the home security specialists — here a steel cable encased in a tough plastic cover links to a small alarm system. A conductive core runs through the cable itself and the alarm is triggered if the cable is cut or the case tampered with; there’s also a movement detection feature which again triggers the alarm if the lock is grabbed or knocked. As you’d expect, the Maxi comes into its own if you’re still within earshot of the bike, maybe in a café or shop, and the 100-decibel alarm is enough to see off shifty-looking types (and local dobermans). 
On its own it could be beaten by a very quick and brazen thief, but teamed with a solid D-lock it makes 
a decent combo. Requires two AAA batteries.