The reason this is so is because the drive is popular as an upgrade to space-constrained Ultrabooks or premium slim laptops that can only carry a single 7mm drive. Identified as ST2000LM007, the bare mechanical spinner is as expensive as the complete enclosure. Seagate achieves such thinness by shoehorning a 7mm-high drive within the case. Reduced thickness is a precursor for a lighter weight the 2TB model chips in at 125g, or about half the weight of a normal drive. At 9.6mm thick, the Ultra Slim, living up to its name, is typically 50 per cent thinner than most standard external 2.5in drives.

The standout feature is the slimness which rivals premium smartphones. An opaque plastic slither in the top-right corner lights up white when power is fed to the Ultra Slim. Going thin means the aluminium cover is thin enough for the drive's vibrations to be felt even when it's idling. Offered in 1TB (£55) and 2TB (£85) capacities and in either platinum or gold, the golf ball dimple-like finish is decent rather than ultra-premium. This is the realm of the Seagate Backup Plus Ultra Slim duo of drives. Or, if travel weight and absolute form factor are important, a premium can be paid for a slimmer, sexier unit. So why would you pay extra? More capacity is a good reason these 2.5in drives can be had in up to 4TB packages. There's little need for the faster USB 3.1 conduit because mechanical drives aren't able to saturate the real-world 400MB/s available on the older standard. Laying down £60 is enough budget to secure a 2TB 2.5in external drive connecting to the system via ubiquitous USB 3.0. That said, the humble, usurped mechanical disk still holds sway where capacity is key, most notably in NAS devices and external storage.

Reasons are simple enough: electric speed, great response times, shockproof construction and, now, usable capacities at reasonable prices. We've been staunch advocates of solid-state drives.

Seagate backup plus slim for mac review