By Frank Dalleres Roger Federer, perhaps the greatest men’s tennis player of all time, has announced that he will retire from the sport after this month’s Laver Cup in London. The 41-year-old, who won 20 Grand Slams including a record eight men’s singles titles at Wimbledon, said it was “time to end my competitive career”. Federer had a third round of knee surgery this summer and admitted he had struggled to make a full recovery. “I’ve worked hard to return to full competitive form,” he added. “But I also know my body’s capacities and limits, and its message to me lately has been clear.” The S…