this film. Yates and Heyman have noted that some of the events of Harry Potter and the Deathly Hallows influenced the script of Half-Blood Prince. Christian Coulson, who played the young Tom Riddle in Chamber of Secrets, expressed interest in returning for the role in flashback sequences; but Yates responded that Coulson was too old (nearing 30), to be playing the role. Thomas James Longley was the original choice to take on the role, but Riddle was ultimately played by Hero Fiennes-Tiffin as a child and Frank Dillane as a teenager. Helen McCrory appears as Narcissa Malfoy, Draco's mother and younger sister of Bellatrix. McCrory was originally cast as Bellatrix in Order of the Phoenix, but had to drop out due to pregnancy. Naomi Watts was previously reported as having accepted the role, only for it to be denied by her agency.<ref name="mtvwatts">{{cite news |title='"'Harry Potter Casting Rumors Untrue, Say Actors' Reps |url=http://www.mtv.com/news/2428894/harry-potter-casting-rumors-untrue-say-actors-reps/ |access-date=4 January 2022 |date=25 July 2007 |last=Adler |first=Shawn |publisher=MTV |url-status=dead |archive-url=https://web.archive.org/web/20070805121548/http://moviesblog.mtv.com/2007/07/25/harry-potter-casting-rumors-untrue-say-actors-reps/ |archive-date=5 August 2007}}</ref> Both Clémence Poésy and Chris Rankin, who had played Fleur Delacour and Percy Weasley, respectively, were interested in returning, but did not appear in the film. After Bill Nighy expressed an interest in appearing, Yates confirmed that Nighy would be his first choice for the role of Minister for Magic Rufus Scrimgeour. Scrimgeour's character was ultimately cut from the film, but Nighy appeared in his role in Deathly Hallows. Warner Bros and MSN also ran an online Order of the Phoenix quiz, with the prize being a walk-on part in the Half-Blood Prince. Sets Stuart Craig, the production designer of the first five films, stayed on to design all the sets in Half-Blood Prince. Several new sets were introduced, including Tom Riddle's orphanage, the Astronomy Tower, and the cave. Craig noted that the film used several CGI sets, noticeably the interior of the cave where Harry and Dumbledore both go to hunt Horcruxes. The exterior of the scene was filmed at the Cliffs of Moher in the west of Ireland, the only location to be filmed outside of the United Kingdom throughout the film series. The interior of the cave is made up of geometric crystal formations. Radcliffe said that the scene took three-to-four months to prepare. Some of the Hogwarts sets were taken down after the filming, as they would not be used for the following film. Filming Before filming began, there