Closed on Friday, open on Monday. In between lies a whole weekend.

Fewer than you'd think, because in an empty hall a motion detector sees a long way. Two to three cover the entire space in most commercial buildings, provided you mount them high and aim them along the walkways instead of at a shelving unit. If there are tall racks, keep in mind that they block the view: then you're better off placing a detector per aisle than one in the middle. On top of that, put a contact magnet on every door someone could get in through, including the emergency exit.

With most business insurance policies, the excess alone is higher than what a complete system costs, and that's before counting downtime: a day of not being able to deliver often hurts more than the stolen goods themselves. Here you pay once and nothing more — no subscription that renews every year, and if you move, the system simply comes with you to the new premises.

That depends on your policy, and the honest answer is: probably not if it includes a certification requirement. Some business insurers require certified security above a certain stock value: approved locks and fittings, installation by an accredited installer and a connection to a monitoring centre. That's where costs rise considerably.

If you want to be well protected yourself and know right away when something happens, this is a great fit. If you need to meet a policy condition, read it first or call your broker — that saves an unpleasant surprise when you make a claim.