DUBAI: Former tennis world number one Serena Williams and seven-times Formula One world champion Lewis Hamilton have joined Martin Broughton’s bid to buy Premier League club Chelsea, a source close to the bid told Reuters on Thursday. Former Liverpool chairman Broughton’s consortium includes World Athletics President Sebastian Coe and wealthy investors from around the world, who the group says all want to maintain Chelsea’s top status. Private equity veterans Josh Harris and David Blitzer, who own sport teams including the National Basketball Association’s Philadelphia 76ers, are also backing Broughton’s bid.