Well, gilt refers to simply the British pound sterling bonds: that is what a gilt is.
It is so-called because when issued, at least originally, they were literally gilt-edged, as in they had a shiny gold colour around the edge.
There is little risk of default on these so they have an excellent rating, well apart from perhaps in credit crunch times post Gordon Brown's influence when it is possible that the government will lose its triple A (AAA) rating!
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