The '80s and '90s saw an arms race between lock makers and bike thieves that eventually settled down when lock makers figured out how to make locks that would resist everything but hefty portable power tools. Here's our selection of the locks that have the right stuff.
A sufficiently determined thief can breach any lock. However, for the best locks 'sufficiently determined' means 'carrying a portable angle grinder'. That's not a cheap tool in itself, and while it's quick, it's also very conspicuous.
One technique of your professional thief is therefore to damage the lock so you can't open it, and then come back late at night with the big guns. If you find your lock mechanism made unusable — filled with glue, for example — break the lock yourself. Hiring an angle grinder will cost you about £20 for the day.
That's about the only way you'll quickly get through most of our lock selection here. The more you pay, on the whole, the longer it takes to breach a lock with unpowered brute force attacks, to the point where a thief won't bother with the best locks, but move on to easier pickings. It's a sad truth that the basis of on-street bike security is to make your bike too much trouble so a thief will nick someone else's.
For 30 quid with a cable to help secure your front wheel the Master Lock Street Fortum is very good value in a lock that meets the Sold Secure Bicycle Gold standard. When we tested it, it resisted bolt-croppers and our persuader test, and the lock mechanism is well-protected from assault.
It can be broken, of course, but if you want a decent level of security at a sensible price for a round-town bike, it's a good choice.
Its RRP is over £40, but the price above is more typical, which makes this tough cookie great value.
The Brute mates a 16mm hardened shackle with a bar made from a single piece of steel, and the locking mechanism is protected against drilling and picking.
In testing it resisted our standard armoury of 3ft bolt croppers, persuader, hammer, cold chisel, screwdriver and hacksaw. The 16mm shackle was too big for the jaws of our croppers so we went after it with the persuader and hammer but after five minutes the damage was pretty cosmetic, and the lock – with a slightly bent shackle – still worked fine.
The Kryptonite New York is plenty tough enough to repel most criminals and is a good choice for everyday use where bike security is a necessity.
It's not cheap, and it's heavy, but the New York pointed and laughed at our standard armoury. Nothing short of some quality power tools would make a dent in this lock.
The Abus Granit X-Plus has long been among the best D locks on the market. It has Sold Secure Gold ratings for both bike and motorbikes (the latter is a higher standard) and it's not hard to see why.
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.
In combination with a hefty chain, a good padlock will provide high-level security for home bike storage, though the substantial total weight makes it a bit impractical as carry-along theft prevention.
The Squire SS50CS is a well-designed, heavily armoured lock that's an excellent partner to some heavy-duty chain.
At 650g it certainly feels the part. It's engineered from a hardened steel billet with a 10mm shackle that's almost fully enclosed. The barrel is protected by another steel plate to protect against drilling, with the key turning just an eighth of a rotation to allow the protective sheet to cover more of the mechanism.
Two metres of Protector 13mm chain weighs 6.95kg so you're not going to be carrying it around, but it's a great last line of defence for your home bike storage.
We couldn't touch it with bolt croppers, and a chain is inherently resistant to prying and hammering, especially a hardened steel chain like this.
Pragmasis offers a package of a 2m Protector with the Squire SS50CS Stronghold padlock above for £123.70.
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Our official grumpy Northerner, John has been riding bikes for over 30 years since discovering as an uncoordinated teen that a sport could be fun if it didn't require you to catch a ball or get in the way of a hulking prop forward.
Road touring was followed by mountain biking and a career racing in the mud that was as brief as it was unsuccessful.
Somewhere along the line came the discovery that he could string a few words together, followed by the even more remarkable discovery that people were mug enough to pay for this rather than expecting him to do an honest day's work. He's pretty certain he's worked for even more bike publications than Mat Brett.
The inevitable 30-something MAMIL transition saw him shift to skinny tyres and these days he lives in Cambridge where the lack of hills is more than made up for by the headwinds.