Exhibition in Madame Tussauds was used. According to producer John Nathan-Turner, Baker had agreed to do the photocall for the 20th anniversary but, suspecting that he might not turn up, Nathan-Turner arranged for the waxwork to be on location. The end credits featured a specially-mixed version of the theme music, which began with Delia Derbyshire's original 1960s arrangement and then segued into the Peter Howell arrangement being used by the series at the time (the former being played at a slightly higher speed to match the tempo and pitch of the latter). This arrangement was only used on this one occasion and was the last time that the Derbyshire version was heard during the show's original run. A unique arrangement of the opening credits music was also used, which ended in a brief coda phrase that was never used in any other serial. Cast notes The First Doctor was played by Richard Hurndall, replacing William Hartnell, who died in 1975. Hartnell does make an appearance, however, in a pre-titles clip taken from the end of The Dalek Invasion of Earth (1964). After initially agreeing to take part, Tom Baker declined to return so soon after his departure from the series two years before, saying in 2014, "I didn't want to play 20 per cent of the part. I didn't fancy being a feed for other Doctors—in fact, it filled me with horror." His appearance was pieced together with footage from the unaired serial Shada. In early drafts of the script, some of the Doctor and companion combinations were different. Originally, the Fourth Doctor would have been paired with Sarah Jane Smith, the Third Doctor with Brigadier Lethbridge-Stewart and the Second Doctor with Jamie McCrimmon. When Frazer Hines, Jamie's actor, proved unavailable for more than a cameo appearance the script had to be altered, pairing the Second Doctor with Victoria Waterfield. This was revised again when Deborah Watling, Victoria's actress, became unavailable and Baker decided not to appear, resulting in the pairings as they were screened. Instead of meeting phantoms of Jamie and Zoe (Wendy Padbury), the Second Doctor and the Brigadier were originally scripted to meet Zoe and Victoria. The Doctor would have realised the truth about them when Victoria called Lethbridge-Stewart "Brigadier", when she only knew him as a Colonel (in The Web of Fear). Deborah Watling was unable to make the recording dates but Frazer Hines was able