Shares in Whitbread rose over 6% to 904p on speculation that the company could be subject to a break up at the hands of venture capital groups, which would value it at £3.5bn.
Whitbread declined to comment on the speculation.
According to a report in the Evening Standard, Apax, CVC and several US buyout firms are considering a takeover move on the group.
Duke Street Capital is said to be among groups sounded out about taking on Whitbread's 65 David Lloyd Leisure clubs, to add to its Esporta fitness business and take on the David Lloyd brand.
Greene King was named as having been consulted about taking on Whitbread's pubs business.
One venture capitalist quoted said: "Any discussion you have with them is met with the response: 'We aren't deciding anything until the new chairman comes in September."
He added: "The sharks are circling. Most people involved can see something will happen before too long."
