Originally, the scenes featuring the Loch Ness Monster were intended to be filmed in the actual Loch. A life-size prop was built which had several Nessie-like humps used to disguise flotation devices. The humps were removed, however, at Billy Wilder's request. Unfortunately, during a test run in Loch Ness, the Monster-prop sank and was never recovered. A second prop, a miniature with just the head and neck, was built, but was only filmed inside a studio tank. Actress Geneviève Page said of this in the biography "Nobody's Perfect: Billy Wilder" by Charlotte Chandler): "When we lost our Loch Ness monster, he [Wilder] wasn't too concerned, even though he was also the producer. He was more concerned about how the man who made it felt when all his work sank to the bottom of the Loch Ness. He went over and comforted him". The original monster prop was located on the bottom of Loch Ness in April 2016 during a survey of the loch by an underwater robot.
With a 260-page script and a budget of $10 million, this was set to be a 165-minute Road Show picture with an intermission for comfort. It was to be the "Big One" for Billy Wilder. The shooting schedule ran for six months and resulted in a rough-cut that came in at three hours and 20 minutes. The film was originally structured as a series of very specifically structured linked episodes, each with a particular title and theme. The opening sequence was to feature Watson's grandson in London claiming his inherited dispatch box from Cox & Co. and there was also a flashback to Holmes' Oxford days to explain his distrust of women. All were shot, but deleted from the final print. So what happened? Well, it appears that United Artists suffered a number of major film flops in 1969 that pretty much scuppered the road show format for Wilder's massive project. Studio execs ordered the film to be cut to fill a regular theatrical running time, whittling it down to a 125-minute version. The episodic format made the pruning process relatively simple, so cut were the opening sequence, the Oxford flashback and two full episodes entitled "The Dreadful Business of the Naked Honeymooners" at 15 minutes and "The Curious Case of the Upside Down Room" at 30 minutes. We can only hope that the full footage can one day be restored, although a full print is not currently thought to exist.
Christopher Lee comes the role of Mycroft with considerable experience in the Sherlock Holmes universe: he previously played Sherlock Holmes and Sir Henry Baskerville. It's been said that Lee is the only, or at least one of few actors, to portray onscreen both Mycroft Holmes and Sherlock Holmes.
Billy Wilder said of this film in the book 'Conversations with Wilder' by Cameron Crowe, "... when I came back [from Paris], it was an absolute disaster, the way it was cut. The whole prologue was cut, a half-sequence was cut. I had tears in my eyes as I looked at the thing...It was the most elegant picture I've ever shot."
By the time of filming, Christopher Lee had become famous as Count Dracula; when he and Billy Wilder walked on the shores of Loch Ness at dusk, with bats circling overhead, Wilder said to him, 'You must feel quite at home here.'
The following have commented on the film's original intended long length and massive editing cut down --- Virgin Film Guide: "The Film was cut by more than thirty minutes by United Artists"; Leonard Maltin: The film was "intended as a 3½ hour film"; Allmovie: "Heavily re-edited and rearranged both before and after its release"; Halliwells: "What started as four stories is reduced to two"; Empire: "Originally a three-hour epic, this 1970 movie was taken from its creator and mutilated by the wholesale lopping of entire episodes".
One of the picture's main movie posters featured a long text preamble that read: "What you don't know about Sherlock Holmes has made a great motion picture. Everyone knows about the lightning-quick mind, the dazzling wit, the magnifying glass. But what about the little glass vials he so cunningly kept hidden. And what about the security blunder that almost cost the British Empire its navy. And what about the woman who spent the night with him".
According to Billy Wilder, since because of schedule conflicts he couldn't himself supervise the bowdlerization of the picture demanded by the Studios, he entrusted the task to the editor, Ernest Walter. Nevertheless, Wilder supposedly strongly disliked the cuts made by Walter, and couldn't re-edit the movie because all the deleted scenes were lost or thrown away. Some of those scenes are available today, but never with both the audio and the video intact.
Around this time, there were also plans to film the Leslie Bricusse musical " Baker Street " which debuted on Broadway in 1965. Fritz Weaver had played Holmes on stage, and Peter Sallis ( of " Wallace and Gromit " fame) was his Watson. Christopher Walken had played one of the villains. Due to its poor performance on Broadway (it played over 300 shows but had been hugely expensive to mount ) and the worry that it would cover much of the same ground as the Wilder project, it never materialised.