Whitbread (>> Whitbread) shares jumped more than 7 percent on Wednesday after U.S.-based hedge fund Sachem Head Capital Management declared a 3.4 percent stake in the British hotel and coffee chain operator.
Whitbread, owner of Costa Coffee and Premier Inn, has been the subject of break-up speculation in the past.
Sachem Head has previously taken activist positions at companies, though it is unclear whether it will push for changes at the FTSE-100 leisure giant.
The hedge fund has already met with Whitbread management, according to a person familiar with the matter.
Before Wednesday's jump, Whitbread shares were down nearly 2 percent this year, having risen in part on hopes that Premier Inn's domestic hotels would benefit from foreign visitors cashing in on the weak pound. They fell back when those benefits turned out to be smaller than expected.
The company warned in April of a tougher consumer environment, as rising inflation and muted wage growth forced consumers to rein in spending.
The shares closed about 7.5 percent higher at 3,990 pence.
Sachem Head, with about $4 billion (£3 billion) in assets under management, was founded in 2013 by Scott Ferguson, one of a number for former partners at Bill Ackman's Pershing Square Capital Management who have launched their own funds.
The New York-based firm has been popular with investors, both because of its steady run of positive returns and the fact Ferguson, who shies away from being called an activist, largely stays out of the headlines.
Ferguson took a board seat at software maker Autodesk (>> Autodesk), and has held sizeable stakes in CDK Global (>> CDK Global Inc) and Zoetis (>> Zoetis Inc). Its current UK holdings include Worldpay Group (>> Worldpay Group) and Shire (>> Shire).
A spokeswoman for Whitbread was not immediately available for comment.
A spokesman for Sachem Head declined to comment beyond Wednesday's regulatory filing, which declared contracts for difference over 6.2 million shares expiring July 2020.
(Additional reporting by Svea Herbst-Bayliss in Boston and Ben Martin in London.; Editing by Mark Potter and Jane Merriman)
By Martinne Geller