The gold reserves of the world’s biggest public sector investors reached an 18-year high as they hoarded the precious metal after Donald Trump’s election and the Brexit vote added to geopolitical uncertainty.

State investors increased their net gold holdings by 377 tonnes to an estimated 31,000 tonnes last year — the highest level since 1999, according to a study of 750 central banks, public pension plans and sovereign wealth funds with $33.5tn in assets.