Sky News has learnt that KSL Capital Partners, the American private equity firm, has been holding talks with prospective advisers about an auction that would kick off either this year or next.
City sources said investment banks including Goldman Sachs were in the frame to oversee the sale process.
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Third Space operates 15 clubs across the capital, including sites in the City and Soho.
They are positioned at the luxury end of the gyms market, offering HYROX, hot yoga and dozens of other classes to members.
KSL acquired a stake in the business in 2021, acquiring a majority stake from Encore Capital, another investment firm.
Last October, Third Space secured £75m in debt finance from Oaknorth, alongside Searchlight Capital, another existing lender, to help fund its expansion.
“We are seeing exceptionally strong demand for Third Space memberships, with most of our clubs operating with waiting lists,” Colin Waggett, chief executive, said last autumn.
“Our business sits at the heart of Londoners’ desire for health and fitness, authentic experiences and luxury service, and Third Space is uniquely positioned to meet these demands.”
KSL and Goldman declined to comment.
