The 5% stake HSBC has built up in Burberry is thought to be on behalf of multiple clients rather than a single investor.
The latest revelation, reported by the Financial Times, puts to rest rumours of a potential takeover bid.
The stakeholding came to light after it rose above the 5% disclosure threshold on February 11 and again on March 1, triggering regulatory filings by HSBC.
Burberry had asked HSBC to reveal the identity of the mystery investor or investors weeks ago, but HSBC refused.
Drapers understands the stake has since dropped back to below 5%.