Public figures who paid tribute include British Prime Minister David Cameron, comedian Ricky Gervais, and authors Ursula K. Le Guin, Terry Brooks, Margaret Atwood, George R. R. Martin, and Neil Gaiman. Pratchett was memorialised in graffiti in East London. The video game companies Frontier Developments and Valve added elements to their games named after him. Users of the social news site Reddit organised a tribute by which an HTTP header, "codice_1", was added to web sites' responses, a reference to the Discworld novel "Going Postal", in which "the clacks" (Discworld's equivalent to a telegraph) are programmed to repeat the name of its creator's deceased son; the sentiment in the novel is that no one is ever forgotten as long as their name is still spoken. A June 2015 web server survey reported that approximately 84,000 websites had been configured with the header.