Farfetch, a fashion startup based in London, has raised a large new round of funding, according to sources familiar with the company. The round, which sources say is worth $40 million, is expected to close this week. Rumors of the company raising $66 million have swirled since March. The company previously raised $42.5 million over three rounds of funding from Index Ventures, Advent Venture Partners, E.ventures, and Conde Nast.