Fans of tennis star Roger Federer will soon have the opportunity to own valuable mementos from his incredible career. The 20-time Grand Slam champion is auctioning off a chunk of memorabilia to raise funds for the Roger Federer Foundation, which aims to give vulnerable children in southern Africa and Switzerland access to a quality education. A live auction is taking place at Christie's London on June 23, with an online auction running from June 23 to July 14. The auction will feature 20 lots from his Grand Slam victories, while a further 300 lots will be part of the online offering. "I started to keep these items from the early days [onwards] with hopes of, one day, doing something that can help make a difference in the world," Federer said. The items include a racket bag and shirt from the 2006 Wimbledon tournament, where Federer defeated Rafael Nadal in the final to claim his fourth consecutive Wimbledon crown. The estimated price is £15,000-25,000. Federer made it five in a row the following year and an outfit and Wilson racket from this success is estimated to go for £30,000-50,000. There's also a pair of "Darth Federer" Nike night sneakers from the 2007 US Open which are expected to raise £15,000-25,000, and another pair of signed Nike shoes are set to raise £50,000-70,000. The online auction items include outfits, bags, headbands and a classic Wimbledon tournament towel. Christie's low estimate values the entire collection at £1 million.