The total percentage of Royal Mail’s stock being shorted down from 10% in August to 1% today and the share price, up 21p to 274.25p, has rallied since lows of 124p in March.
That was boosted when Czech energy tycoon Daniel Kretinsky increased his stake in the firm dramatically.
His intentions are unclear although some have said he may be seeking to carve up the business and buy its overseas arm, GLS. Others have said he simply sees Royal Mail as an undervalued business.
Share trading today saw volumes of triple its usual level amid frenzied demand for stock.
They have fallen sharply since 2018 as demand for letters has gone into freefall.
Royal Mail is one of the widest held shares by private investors.