Hedge fund Elliott Advisors is reported to be demanding that Whitbread spin off its Costa coffee chain.
Elliott Advisors, who have built up a stake of more than 6% in the company, want the coffee business to be separated from Whitbread's Premier Inn chain, The Sunday Times reported.
The reported pressure from the company's largest investor comes after Whitbread's chief executive has indicated she was "open minded" to changes in the company's structure.
Elliott is said to believe the split could create as much as £3bn in value.
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