David Niven was unhappy at being forced to make this film, and later cited this as a reason for severing his contract with Samuel Goldwyn. For a long time Niven had disliked the films he was being cast in by Goldwyn. They had a furious row in which Goldwyn threatened to destroy Niven's career in Hollywood, while Niven accused the producer of making a fortune from him while loaning him cheaply to other film studios.
Originally planned as a musical, and was to have been co-produced by Samuel Goldwyn which would have helped its distribution in the United States. After he pulled out, Alexander Korda (the executive behind "London Films") sued him. The movie was finally distributed in the States by "Carroll Pictures" in black and white only.
Although filmed in 1948, the movie did not have a US release until 1954. This was because Samuel Goldwyn considered it to be terrible and refused to release it. He was sued by Alexander Korda as a result, and Goldwyn then counter-sued Korda.
The fact that this version of the Scarlet Pimpernel story was planned as a musical is evident from even a cursory viewing of this movie. There are multiple scenes which seem chopped short or disjointed from the editing which apparently occurred to cut out scenes in which singing was involved.