In February 2016, Helga Kern boarded a plane to Iran, registered with the depository to trade stocks and within weeks opened a broker account and started buying shares, all with the aim of launching an Iran fund for Western investors.

But on the eve of Friday's presidential election in Iran, Kern, who is a managing partner at Swiss fund advisory firm KK Research, has little hope that other investors will emulate her dash into the oil-rich country which had appeared on the verge of ending three decades of isolation.