not a Wedgwood piece I'm fairly sure. Susan Tobin writes (re Charles and Diana Royal commemoratives) that..........."The only item unique to the collection was the first and only two-handled loving cup made by Wedgwood Glass. It was amethyst with clear glass handles etc.".
It's sort of tankard shape with two large looping handles, not like your piece, unfortunately.
Although Dartington made some Indigo pieces, I think the colour of this one is too dark for that.