Could the most lucrative investment portfolio you own be hiding in your closet? Important fashion items from the 20th century are fetching record prices at auction, and estimates at a number of high-profile sales this autumn look set to push prices even higher.

In 2011, a gold commodities trader paid $1.8m for Michael Jackson’s jacket from the “Thriller” video at a sale by Los Angeles-based entertainment auction house Julien’s. Darren Julien, the house’s chief executive, says investors and hedge funds are looking at fashion as a way to diversify from other hard goods, such as art, as fashion “will turn a profit over five years and shows wealth and status in the office while it appreciates”.

Celia Joicey, head of London’s Fashion and Textile Museum, which experienced an 87 per cent year-on-year increase in visitors to August 2013, says: “Fashion was given a value the minute it went into the museum space, with prices rising alongside the soaring visitor figures.”