Like many other mints, the Royal Mint issues bullion coins in precious metals, having much higher intrinsic value than their face value. Most of these by tradition are measured in troy ounces of fractions thereof, but the mint also introduced metric coins measuring one kilogram of pure metal (they are actually fractionally heavier as a whole, to account for the small amount of other metal in the alloy).
The 1 kg gold coins are denominated as One Thousand Pounds (£1,000), although their intrinsic (bullion) value is much higher than their face value. The coins vary in design depending on the occasion (they are "one-year" types usually issued in parallel with smaller denominations with the same reverse designs).
The coins are legal tender but are not intended for circulation. They are targeted at bullion investors or collectors who appreciate the special editions as pieces of art.
This coin is part of the fifth edition of the Great Engravers series of re-issues of past masterpieces, and features the classic St George and the Dragon reverse.
The design was developed by Benedetto Pistrucci for the first gold sovereign in 1817; this edition pays tribute to its slightly re-worked version as seen on the 1818 silver crown. More than two centuries later, the design is still in active use - it is the definitive design for the gold sovereign, albeit minus the garter (the change was made in 1821).
The Royal Mint says about it:
Displaying all the power and poise of neoclassicism, Benedetto Pistrucci’s St George and the dragon design is a remarkable work, considered by many to be his best design. We pay tribute to the artist’s abrasive genius with a modern interpretation of a numismatic masterpiece. The recreation of the raised edge lettering is a remarkable technical achievement. | 
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