Private equity group Alchemy Partners, which owns a majority stake in Cathedral, is putting the business on the block six and a half years after it first invested in the company, the source said, asking not to be named. Cathedral's senior executives own the remaining 37 percent of the firm.

Information memorandums on Cathedral, founded in 1997, are expected to be distributed to potential investors next week, the source also said.

The Lloyd's of London insurance market, which started out 324 years ago as a gathering of shipping merchants in a London coffee house, represents the combined results of about 80 competing insurance and reinsurance syndicates.

Cathedral is not the first company with a presence on Lloyd's to have attracted the interest of private equity owners. Brit Insurance was bought by Apollo and CVC in 2010.

Listed companies which operate syndicates at Lloyd's include Catlin (>> Catlin Group Limited), Hiscox (>> Hiscox Ltd) and Amlin (>> Amlin plc).

Alchemy declined to comment. Cathedral was not immediately available for comment.

News of the sale was first reported by Sky News.

(Reporting by Tommy Wilkes; Editing by Alex Smith and Mark Potter)

Stocks treated in this article : Amlin plc, Catlin Group Limited, Hiscox Ltd