The stake is believed to be worth up to£170 million, or 3 per cent of M&S. The food and clothing retailer experienced a gain of 5.25p yesterday and M&S shares have risen a further 4p since the market opened today.
Dealer speculation has focused mainly on Icelandic retail giant Baugur, which owns a raft of UK high street names, including Iceland, Karen Millen and Oasis. Baugur boss Jón Ásgeir Jóhannesson is understood to have acknowledged that M&S has value for his company. However, there has been no confirmation that Baugur is the investor. The other company in the frame is investment bank Kaupthing.
The share jump will be welcomed by M&S investors, who shunned a potential offer from billionaire tycoon Philip Green 12 months ago valuing the company at 400p a share offer.