Apple has unveiled its new iPad, the first of its tablets to boast a Retina display alongside an update to iOS 5.1, which is available for download today.

Apple CEO Tim Cook unveiled the new device at an event in San Francisco, which has the same size display - 9.7in - as its predecessors, though has a resolution of 2048 x 1536, cramming 3.1 million pixels onto the screen at 264 ppi (pixels per inch).

And in a move that'll confound those who confidently predicted that it'd be called the iPad 3 or iPad HD, the new device will be known simply as the iPad.

"Until you see it, you can't understand how amazing it is," Cook said. It'll be available in the UK from Friday 16 March with pre-orders beginning today.

Apple first introduced the concept of a “Retina display” in the iPhone 4, which packed 326 pixels per inch into its 3.5-inch display. Rather than refer to a specific level of pixel density, the term defines how the average person sees a screen—at a certain distance away, the human eye can no longer distinguish the individual pixels on a device.

Although the new iPad has a lower pixel density (264 versus 326) than the iPhone 4 or 4S, that’s largely due to screen size and relative distance—users hold the iPad further away from their faces than they might an iPhone.

There's an A5X processor twice as fast as its predecessor and the graphics performance is up to four times that of the iPad 2, Apple's Phil Schiller said.

The iPad now sports a 5-megapixel iSight camera with a 5-element lens, IR filter, and in-plane switching built into the iPad’s new chip. Schiller said the new iSight camera has automatic exposure and auto-focus, and now records HD video at 1080p resolution. Like the iPhone 4S’s camera, the iPad’s camera features automatic face detection, automatic exposure lock, and automatic focus lock. Also thanks to the new A5X chip, Schiller said, you also get image stabilization.

Apple historically doesn’t discuss details like the amount of RAM built into its iOS devices. The iPad 2 offers 512MB of RAM, doubling the original iPad’s 256MB. It’s not yet clear whether the iPad doubles the memory size again.

It also brings support for 4G LTE next-generation mobile data service – which offers download speeds many times faster than 3G – though this isn't going to be much use to those of us in the UK as Ofcom won't even start the auction for the LTE spectrum until the end of the year, and it won't be available to consumers until well into 2013 at the earliest.

However, it does also bring support for HSPA+, a wireless standard with a maximum downlink speed of 21Mbps, and DC-HSDPA, another flavour of 3G, which has a maximum downlink speed of 42Mbps.

New to the iPad is a microphone button on the virtual keyboard, one that looks just like the corresponding icon on the iPhone 4S’s keyboard. You can use that microphone for dictation anywhere the keyboard appears. That’s obviously short of full Siri integration.

It's 9.4mm thick - which is slightly chunkier than the iPad 2's 8.8mm thickness - and weighs 635g, slightly more than the 601g of the iPad 2 Wi-Fi only and 613g of the iPad 2 3G and Wi-Fi model.

It comes in black or white and comes in Wi-Fi only or Wi-Fi + 4G models. Battery life is claimed to be 10 hours for the Wi-Fi only version, nine hours for Wi-Fi and 4G.

It will go on sale in the UK, Canada, US, France, Germany, Switzerland, Japan, Hong Kong on 16 March and in 25 other countries one week later.

The new iPad Wi-Fi models will be available in black or white on Friday 16 March for a suggested retail price of £399 inc VAT for the 16GB model, £479 inc VAT (for the 32GB model and £559 inc VAT for the 64GB model. iPad Wi-Fi + 4G will be available for a suggested retail price of £499 inc VAT for the 16GB model, £579 inc VAT for the 32GB model and £659 inc VAT for the 64GB model.

iOS 5.1 introduces new feautres including Japanese language support for Siri, a new camera access mode on the home screen, and several performance enhancements. iOS 5.1 is expected to be available via iTunes and within iOS Software Update later today.

Schiller also said that Apple is offering updated versions of its iWork suite for the Retina display, a new version of iMovie with support for movie trailers, an update for GarageBand that adds the ability for four iOS device users to jam together, and a new app: iPhoto for iOS.

Click here to read more about the Apple TV 3

Click here to read the Live Feed from the 7 March event