Jane is also mindful of not having too much exposure to any individual currency, though at present he has a lower-than-usual exposure to sterling, given volatility of the UK currency at present 

But Clive Emery, multi-asset investor at Invesco, says the evidence of this year so far is that currency exposure may not be all that it seems.

He says: “Global equities are down around 23 per cent in US dollar terms, so one may have reasonably expected that more cautious portfolios should have outperformed the more aggressive equity-biased portfolios. However, currency has had a huge impact on overseas equity returns this year.

"Many investors are exposed to global equities on an unhedged basis currency perspective, meaning that many UK-based investors have benefitted from a weaker sterling.

"With sterling falling from $1.35 to $1.13 against the US dollar this year, the difference in returns has been quite stark – that 23 per cent loss in US dollar terms has been just an 8 per cent loss in sterling terms.

"So, cautious portfolios with significant exposure to duration may have significantly underperformed more aggressive portfolios. I think that this context has a lot to do with why cautious portfolios are now being called into question.”

David Thorpe is special projects editor at FTAdviser