Prince William is the 1,000th member of the register of the Order of the Garter, and was officially invested by the Queen on 16 June 2008 at a service at St George's Chapel, Windsor Castle.
The last time a monarch appointed a grandchild into the Order of the Garter was in 1894, when Queen Victoria invested Alfred, Hereditary Prince of Saxe-Coburg and Gotha.

23 April 2008: Royal Knight Companion of the Most Noble Order of the Garter (KG)
25 May 2012: Extra Knight of the Most Ancient and Most Noble Order of the Thistle (KT)
Prince William is the 1,000th member of the register of the Order of the Garter, and was officially invested by the Queen on 16 June 2008 at a service at St George's Chapel, Windsor Castle. The last time a monarch appointed a grandchild into the Order of the Garter was in 1894, when Queen Victoria invested Alfred, Hereditary Prince of Saxe-Coburg and Gotha.
23 April 2008: Royal Knight Companion of the Most Noble Order of the Garter (KG)
25 May 2012: Extra Knight of the Most Ancient and Most Noble Order of the Thistle (KT)
Prince William, Duke of Cambridge