Mac OS X 10.7 Lion is now available to download through the Mac App Store. You won't find Lion on the front page of the Mac App Store, though, but you can locate it by using the search function.

Apple finally unveiled its long-awaited update to the Mac OS after chief financial officer Peter Oppenheimer let slip that it would launch today in last night's third-quarter financial earnings call.

“Lion is the best version of OS X yet, and we’re thrilled that users around the world can download it starting today,” said Philip Schiller, Apple’s senior vice president of Worldwide Product Marketing.

“Lion makes upgrading a Mac easier than ever before; just launch the Mac App Store, buy Lion with your iTunes account, and the download and install process will begin automatically.”

There are a whole host of new features in Mac OS X 10.7 Lion, including support for new Multi-Touch gestures such as momentum scrolling, tapping or pinching your fingers to zoom in on a web page or image, and swiping left or right to turn a page or switch between full screen apps.

There is support for full screen apps, meaning you can swipe from one window to another, between full screen apps, or back to your Desktop, Dashboard or Spaces without ever leaving full screen.

Also new to Lion is Mission Control, which provides and overview of everything running on your Mac, combining Exposé, full screen apps, Dashboard and Spaces into one unified experience.

The Mac App Store will be built in to the OS; Launchpad, a new home for all your apps where a single Multi-Touch gesture presents all your Mac apps in a full screen layout, is another new feature and there is a completely redesigned Mail app.

The new Conversations feature groups related messages into an scrollable timeline, hiding repeated text so the conversation is easy to follow, and retaining graphics and attachments as they were originally sent.

Lion costs £20.99 and is only available through the Mac App Store on Macs running OS X 10.6.6 or higher. It is a 4GB download.

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You'll need a Mac with a dual- or quad-core Intel processor, such as the Core 2 Duo, Core i3, Core i5, Core i7 and Xeon to run Lion. Like Snow Leopard , Lion won't run on the PowerPC architecture that Apple abandoned in early 2006 when it started the switch to Intel CPUs. 2GB of RAM is also a minumum.

If you bought a Mac after 6 June you will be eligible for a free upgrade to Mac OS X Lion 10.7. Mac OS X Lion Server requires Lion and is also available in the Mac App Store for £34.99.