(digitalspy.co.uk ) - Robbie Williams will reportedly sing at golfer Colin Montgomerie's wedding, The Mirror reveals.Williams has been friends with the Scottish sports star since the pair met at a celebrity golf tournament three years ago. Montgomerie's wedding to Gaynor Knowles will take place later this month on the banks of Loch Lomond.Montgomerie remained tight-lipped about his wedding, saying: "I can't say anything - I am not allowed to say anything. But this will be an event. This will be an extraordinary event."The ceremony has a guest list of 400 with Chris Evans, Hugh Grant and Prince Andrew all thought to be attending.Recent reports claimed that Williams donated cash to NASA to help them prove aliens live on Mars.