When selling something at auction, the guide price is usually set by the auctioneer, who makes a guess based on what similar items have fetched in the past. But for rare or unusually expensive items, a specialist valuer is called in to estimate the price.

This is how areas of the corporate bond market have been functioning for months. The guide price is not as accurate as it used to be and the price last paid is no longer a reliable source. With UK corporate bond funds operating similarly to emerging market equity portfolios, managers are unable to price some holdings and are reliant on data that cannot always be trusted.