Ultrabooks are more than a simple size-zero battle of aggressive laptop dieting, but that hasn't stopped manufacturers from battling it out for the 'World's thinnest' accolade. The Asus Zenbook UX31E, Acer Aspire S3, Dell XPS 13 and Samsung Series 9 have all come close, but now the Acer Aspire S5 takes the low-fat cake.

The Acer Aspire S5 is the second Acer Ultrabook to hit the market since the birth of the Ultrabook, and with the huge price drop for its little brother the Aspire S3, there's a clear strategy in place. You can pick up an Acer Aspire S3, with a small SSD and a 500GB HDD for just over £600 in the UK or just under $700 in the US, making it one of the cheapest Ultrabooks.

Acer Aspire S5 review

The Acer Aspire S5, however, sits at the other end of the scale, with the eye-watering price tag of £1,249.99/$1,399.99. That's within small change of the best Apple MacBook Air on the Apple Store - but don't get us wrong, this is no clone.

The differences are immediately apparent, with a metal finish coloured in a satisfying black, which is cool to the touch and light-years apart from the MacBook Air.

Its slick onyx black magnesium-aluminium chassis acts as a deceptive cage for the slender beast within – it's only when you pick up Acer's new baby that you realise just how lean and light it really is – 1.2kg (2.65lbs), in case you were wondering.

Acer Aspire S5 review

The price is high, but there's a real difference between this and many of its competitors. There's little pay off between the build and power, and for once, you get the feeling that the Acer Aspire S5 earns its price tag.

As well as being extremely light, it's also frighteningly thin. It measures just 15mm (0.59 inches) and there's no tapering off to a thin point like there is on the MacBook Air, which gives the illusion of thinness despite being nearly 2cm (0.79 inches) thick at the hinge side. If the Acer Aspire S5 were a teenager, it would be immediately sectioned as a risk to itself.

With all that considered, it's time to get under the hood and put this super-slim Ultrabook through its paces.