Two 50p coins were issued dated 2008, one of the standard (old) Britannia design and another of its replacement standard (new) design featuring the bottom section of the Royal Coat of Arms.
The story behind the design:
The obverse portrait of the Queen by Ian Rank-Broadley was used on all UK coinage from 1998 to 2014 and for some 2015 coins. It was the fourth portrait of the Queen used on coinage.
The reverse design, by Christopher Ironside, shows Briannia seated. Britannia had appeared on at least one British coin denomination since the 1670s, and in fact long before that there were Roman coins showing the word ‘BRITANNIA’ and the helmeted female representation of Britannia to celebrate the Roman capture of Britain.