There have been plenty of unlikely friendships within celebrity circles over the years, and another one to add to that list is Russell Crowe and Lord Alan Sugar.The business tycoon, who previously engaged in a Twitter row with Piers Morgan's mum, was spotted playing a game of tennis in Australia with the award-winning actor.The pair were joined by Alan's wife Ann Simons and Russell's girlfriend Britney Theriot as they spent some quality time together in Sydney.