The Wellcome Trust, the UK's largest charity, has emerged as the mystery investor that has been building a stake in Marks & Spencer.
The Wellcome Trust, a medical research charity, has taken a 2.5% shareholding the high street retailer, acquiring 39.35 million shares.
The stake is thought to be worth about £100 million and comes just a month after M&S issued a profit warning.
In a statement, The Wellcome Trust said the investment was part of its "long-term investment portfolio".
The Wellcome Trust is an independent charity funding research into human and animal health. The chairty was established in 1936.