Serena Williams returns - why now, and what next?

Serena Williams is doing the unthinkable and returning to professional tennis at the age of 44 after almost four years away from the sport.She announced on Monday that she would be entering the grass court doubles tournament at Queen's - which finishes eight days before Wimbledon - playing with 19-year-old Canadian Victoria Mboko and igniting rumours as to what could be next for 23-time Grand Slam champion.