Like many other mints, the Royal Mint issues bullion coins in precious metals, having much higher intrinsic value than their face value. The one-twentieth ounce (1/20 oz) gold coins are denominated as One Pound (£1) and have been issued since 2013.
These 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. The coins are typically "one-year" types usually issued in parallel with other denominations with the same reverse designs.
Britannia as a symbol has been depicted on British coinage for centuries. The bullion series called Britannia has been issued in gold since 1987 and in silver since 1997; it has a "definitive" depiction - used on bullion coins (Brilliant Uncirculated grade), as well as “Britannia, the Changing Face of Britain” - a series of one-year designs like this one - used on proofs made for collectors.
In 2019, designer David Lawrence offered a second interpretation of Britannia, standing boldly with a lion by her side. This is the second year in a row that he has contributed a portrait of Britannia, lending her an air of consistency as the current and previous incarnations are compared side by side.
David said of his of design, “My initial thoughts were influenced by the great engravers of the past. Their work has a classical grace and gravitas I was keen to recreate. After all, coins of the realm are a serious business. The lion had to be there somewhere, as did the shield and trident... many of the components were already decided in a way. The end result is an Anglicised version of ancient Rome.”
This twentieth-ounce gold proof coin was issued in sets only, not individually. | 
Search for United Kingdom: Gold Twentieth-Ounce 2019 Britannia on eBay 