Sir Peter Hall, director of the National at the time, wrote of Campbell in his Diaries, "He is a total anarchist and impossible to pin down. He more or less said it was a crime to be serious." 
The adaptation became the very first production at the National's Cottesloe Theatre space, running from 4 March to 27 March 1977. It had first opened in Liverpool on 23 November 1976.
The first night of the London version featured Robert Anton Wilson, accompanied by Shea, as a naked extra in the witches' sabbat scene. Wilson was delighted with the adaptation, saying: "I was thunderstruck at what a magnificent job they did in capturing the exact tone and mixture of fantasy and reality in the book. I've come to the conclusion that this isn't literature. It's too late in the day for literature. This is magic!! 
The 23-strong cast featured several actors, such as Jim Broadbent, David Rappaport and Chris Langham, who went on to successful film, stage and television careers. Broadbent alone played more than a dozen characters in the play. Bill Drummond designed sets for the show, and it was eventually seen (when it moved to London, with Bill Nighy then joining the cast) by the young Jimmy Cauty. Drummond and Cauty later went on to form the Illuminatus!-inspired electronica band The KLF.
In thanks, Wilson dedicated his Cosmic Trigger I: The Final Secret of the Illuminati (1977) to "Ken Campbell and the Science-Fiction Theatre Of Liverpool, England." The play was later staged in Seattle, Washington in 1978.
An attempt was made to adapt the trilogy in comic book form beginning in the 1980s, by "Eye N Apple Productions" headed by Icarus!-23. Icarus! met with Wilson in 1984 and subsequently obtained permission from Wilson's agent to adapt the trilogy. Illuminatus! #1 was issued in July 1987, then reissued in substantially revised form later that year by Rip Off Press (who had published the original 4th edition of the Principia Discordia in 1970).
A second issue followed in 1990, and a third in March 1991, after which the venture stalled (although several ashcans of the as yet unpublished Fourth Trip were distributed at comic book conventions in the Detroit and Chicago areas between 1991 and 2006).
Each comic covered one "trip" from the original trilogy, so had further issues followed this pattern, there would have been ten issues in total. The "new first issue" contained a letter from Bob Shea, who had seen the first issue and the materials for the next two. He wrote in part, "I'm delighted. I think it is very faithful to the novel and does a wonderful job of translating the spirit of the novel into a visual medium."  The creators of the comic also made an Illuminatus! discussion room on Citadel bulletin board systems.
InfluenceThe infamous 1980s computer hacker Karl Koch was heavily influenced by The Illuminatus! Trilogy. Besides adopting the pseudonym "Hagbard" from the character Hagbard Celine, he also named his computer "FUCKUP," after a computer designed and built by that character. He was addicted to cocaine and became extremely paranoid, convinced he was fighting the Illuminati like his literary namesake. In 1987 he wrote a rambling seven-page "hacking manifesto of sorts, complete with his theories on Hagbard Celine and the Illuminati." The 1998 German motion picture 23 told a dramatized version of his story; Robert Anton Wilson appeared as himself.
A card game inspired by the trilogy, Illuminati was created by Steve Jackson Games. Using the Illuminatus! books as "spiritual guides but not as actual source material," it incorporated competing conspiracies of the Bavarian Illuminati and Discordians and others, though no characters or groups specific to the novels. A trading card game (Illuminati: New World Order) and role-playing game supplement (GURPS Illuminati) followed. The instruction booklets' bibliographies praise the novel and Wilson particularly, calling Illuminatus! in part "required reading for any conspiracy buff". Robert Shea provided a four-paragraph introduction to the rulebook for the Illuminati Expansion Set 1 (1983), in which he wrote, "Maybe the Illuminati are behind this game. They must be—they are, by definition, behind everything." Despite this initial involvement, Wilson later criticized some of these products for exploiting the Illuminatus! name without paying royalties (taking advantage of what he viewed as a legal loophole).
The Illuminatus Trilogy! is steeped with references to the 1960s popular music scene (at one point a list of 200 fictional bands performing at the Walpurgisnacht rock festival is reeled off (including a handful of actual bands of the 60s), and there are numerous references to the famous rock and roll song, "Rock Around the Clock"), and has influenced many bands and musicians. One of the aliases of anarchic British band The KLF was named after a secret society from the trilogy. They released much of their early material under the name "The Justified Ancients of Mu Mu"/"The JAMMs", cf. "The Justified Ancients of Mummu"/"The JAMs" from the trilogy, and much of their work was Discordian in nature. They mirrored the fictional JAMs' gleeful political tactics of causing chaos and confusion by bringing a direct, humorous but nevertheless revolutionary approach to making records. The American band Machines of Loving Grace took the name of a sex act performed by one of the main characters during a Black Mass for the title of their song "Rite of Shiva" on their eponymous album. UK chillout maestro Mixmaster Morris also named his band The Irresistible Force after one that appears at the festival in the last part of the trilogy. Together with Coldcut he organised a huge Robert Anton Wilson Memorial Show at the Queen Elizabeth Hall in London on 18 March 2007.
In general, The Illuminatus! Trilogy can be credited with popularizing the genre of conspiracy fiction, a field later mined by authors like Umberto Eco (Foucault's Pendulum) and Dan Brown (Angels and Demons, The Da Vinci Code, The Lost Symbol), comic book writers like Alan Moore (V for Vendetta, From Hell), Dave Sim (Cerebus) and Grant Morrison (The Invisibles), and screenwriters like Chris Carter (The X-Files) and Damon Lindelof (Lost). In particular, the regular use of the Illuminati in popular culture as shadowy central puppet masters in this type of fiction can be traced back to their exposure via The Illuminatus! Trilogy.
...in memoriam Ken Campbell 1941-2008...
...if you can't wait for the next thrilling trip, get the whole thing unfiltered here...
...and for you readers out there, get the pdf here...