How long do you have to be hacking away at bike lock before someone asks you what’s going on? As much as three minutes if this video from a couple of students at Nottingham Trent Uni is anything to go by.

As part of a design project, the students thought they’d find out how long you can spend attacking a bike lock before someone notices and has a word with you.

Mocking up an attack on a lock with a blunt hacksaw, the students made no attempt to conceal what they were doing - no boltcroppers hidden under a long coat here, one of them simply went at it with the saw till someone asked what was going on.

The average time they went unmolested was 2 minutes 22 seconds, but in one sequence the ‘thief’ spent three and a half minutes going at the lock while being filmed from a discreet distance. He actually starts to look pretty bored.

Two minutes doesn’t sound very long, but Stephen Briggs of bike security company Pragmasis says it’s plenty of time for a skilled thief to take off with your bike.

Stephen told us: “Most bikes are 'locked' with cable locks, and you can cut through most of the unarmoured ones with a junior hacksaw, like he used (albeit not blunt) in less than 30 seconds.

“If you use the sort of cable cutters you can get from Machine Mart etc for around £15, you can cut them all in about a second. Even the armoured ones are mostly easy to defeat with cable cutters or bolt croppers or hammers.”

Between that information and the video, the advice is simple: steep clear of cables of any sort as your main lock.

A chain or D-lock is a far better bet, says Stephen, though the quality there is variable, and the way you use them makes a big difference. “Our chains have to survive a 5-minute sawing test for the Sold Secure Bicycle Gold approval, and that's when they're held in a vice,” he says.

“However, thin chains (10mm or less) are all relatively easy to cut with bolt croppers. Bicycle thieves tend to use small croppers (e.g. 18in or 24in) that are quite limited in the amount of leverage they can exert, but having a chain anywhere near the ground makes the croppers much easier to use.”

That’s because if a chain is close to the floor, the thief can rest the cropper on the floor and use all his weight to cut the chain.

Badly used, a thin (under 8mm) or low quality chain is again seconds work for a thief with croppers.

“A good chain, 10mm+, up high, is a much tougher target for thieves,” says Stephen. “We don't guarantee it, but we'd expect our 11mm chain to stop 24" croppers, even if it is lying on the floor.”

What about D-locks, long considered the gold standard of bike security?

“Cheap ones can be broken easily with twisting/levering attacks if you don't fill the space inside the 'D' thoroughly and if there is something to lever against (e.g. railings, Sheffield stand, even the bike),” says Stephen. “Medium D-locks can be cut with hacksaws & bolt croppers similar to chains.”

Buy a good one, then, and fill it with the bike and whatever you’re locking it to. That’s a point Stephen was very keen to emphasise.

“It is vital that it is used to lock the bike to something solid, and not another bike!” he says.

“We've had cases of frames being cut to release another bike. This is another type of attack that can be fast and quiet, taking e.g. 30 seconds to hacksaw through the frame of a bike to steal it (for its components) or to steal an attached bike (with the chain etc still attached).

“Putting the chain/D-lock through the main triangle of the frame and the rear triangle and the rear wheel, and locking the bike to a Sheffield stand etc that is genuinely solid, deters these component/secondary attacks.”

“All in all,” he add, “most bikes that get nicked are stolen easily and in seconds, and passers-by won't take any notice. People need to take responsibility for their own security and match the deterrent to the nickability of the items concerned.”

This isn’t the first mocked-up bike theft video we’ve brought you. Last year police in Cambridge — the bike theft capital of the UK — demonstrated just how easy it is to steal a bike. Security company Bike Dock Solutions also has a video demonstrating how little notice passers-by take of thieves.

Last July, London police produced two useful videos about bike theft.

Over the years we’ve compiled what we think is the definitive set of anti bike theft tips, with input from the road.cc community, and much of it aligns with Stephen Briggs’ advice, so here it is again to cut out and keep.

The road.cc community Bike Locking Bible