First published by Money Metals here: https://www.moneymetals.com/news/2018/06/26/us-gold-exports-to-london-surge-001560

As U.S. gold exports to Hong Kong and China fell 25% in the first four months of the year, London picked up the slack. According to the USGS, U.S. gold exports to London surged more than doubled from January to April, compared to the same period last year. Interestingly, the amount of gold exported to London during this period nearly equaled the total U.S. domestic gold mine supply.