This coin is known as the Una and the Lion Five Pound piece.
It was ultimately derived from a poem, The Faerie Queene by Edmund Spenser in praise of Queen Elizabeth I published in 1590. In that poem Una is the personification of the "True Church" and also representative of Truth. At one she point tames a lion by her beauty and honesty; the lion then travels with her both as a guard and to undertake deeds.
On the coin, by William Wyon, Una is Queen Victoria. She is wearing a crown and guiding the lion with her sceptre while holding an orb.
It is a classic of the Victorian Age in both style and sentiment, and one of master engraver William Wyon's masterpieces, with a modest mintage in the hundreds. It was only minted on demand from the time it first appeared in the Coronation sets.
This large, glamorous type always makes the front cover of any auction catalog in which it appears.