Abus Granit X-Plus  £69.99

The Abus Granit X-Plus has long been among the best D locks on the market, it has a Sold Secure Gold rating and it's not hard to see why.

The shackle is made from 13mm square section hardened steel, and locks at both ends to the base. It has pointed ends which extend right through the base to protect against attacks from jacks, and the square section is intended to make it harder to twist or crop. You can get a couple of different mounts, ours came with the frame mount that has a positive locking action and secures via a webbing strap. You get two keys, one with an LED light which is a useful touch.

We gave it a good go (five minutes of serious abuse), but to no avail: we couldn't break this one with our standard thieves' armoury. The shackle is super stiff and no amount of cropping, twisting or thwacking would do any serious damage. the plastic sleeve got a bit mangled, but that was about it. Some meaty blows to the base broke off the plastic covering, but only to reveal a serious looking steel plate construction that does a very good job of protecting the lock mechanism and was dismissive of our efforts: after all the violence was over the lock was still in perfect working order, even the plastic cover just snapped back on.

As we've said, we used all our standard kit on the Granit X-Plus and it came through unscathed - we didn't go the whole hog though and use the 'extreme kit' one of the latest generation of battery powered angle grinders simply because we know what the outcome would have been - a broken lock. We know of no D-Lock that will currently withstand assault by power tool.

No doubt the lock manufacturers are on the case to rectify that. However it has always been the case that given time and sufficient fire power a really determined thief will get your bike. Luckily there are few such thieves about and locks don't give in quietly when attacked with an angle grinder.

It's a really excellent lock, this. It's not even that heavy for the amount of protection it provides. Unless you live in a real crime hotspot it should give you all the protection you need.