Like previous versions of the Apple iMac, this latest design is an ‘all-in-one’ computer, meaning the entire system, apart from the keyboard and mouse, is enclosed inside the screen unit.

This top-of-the-range iMac has had some subtle changes made to it, but the big news is it has grown. The screen on the previous model was already an impressive 24in but this new model increases the size to a desk-trembling 27in.

There are two main kinds of flat computer screen and as with the previous model the new iMac uses the better and more expensive IPS type, which provides noticeably improved quality at angles compared to cheaper screens.

The enormous 27in widescreen display has a resolution of 2560x1440 pixels, which is twice what many computer screens have, but the iMac does not take up as much room on a desk as you might imagine. It’s thin, for one thing, and the well-designed stand minimises the room it uses.

The computer contains an Intel Core 2 Duo processor, which is one of the fastest in that range, although not the fastest processor we have looked at recently.

The 4GB of memory is plenty and it comes with a one-terabyte (1,000GB) hard disk, which is enough for all but the very largest music and video collections.

The iMac includes a wireless keyboard and the new buttonless Magic Mouse. Using it soon became fairly easy but despite this, in practice it offers little functionality beyond that of a normal mouse.

Like all Apple computers, the iMac does not use the Windows operating system. Instead it uses Apple’s equivalent, known as Mac OS X.

It’s an elegant alternative to Windows and includes Apple’s iLife 09 collection of programs. This bundle includes great photo-organisation, web-design and video and sound-editing applications. It’s almost everything a home user needs, ready to go.

If you’re a PC user, it’s not hard to get used to the Mac’s operating system. In fact it’s set up to be easy to use and your old documents will still be useable.

The iMac was almost silent in operation and it’s not short of connections and ports: there is a webcam and an SD memory card reader built into the case, along with four USB sockets, a Firewire port, and connections to Bluetooth, wired and wireless networks. If you have other modern Macs the screen can even be used as a display for them, using its Displayport socket.

At £1,349 the 27in iMac is not cheap. However, with the quality and size of the screen, the included software and the strong residual values are all taken into account, the iMac actually represents fair value for money. While this 27in model is overkill for many, power users will love working with so much space on the screen. For them, this iMac is likely to represent a substantial, yet worthwhile, investment.