The Finnish B-movie, which sees exiled Nazis on the moon return to Earth in the year 2018, had been scheduled for a one-day release today (May 23) before bowing on DVD, Blu-ray and download on May 28.
Director Timo Vuorensola's sci-fi film had been due to screen at more than 30 UK locations for an exclusive one-day window, but will now continue to play at selected cinemas for as long as demand dictates. The home release remains May 28.
Ben Freedman, owner of London's Prince Charles Cinema, said that he had been in ongoing discussions with distributor Revolver to keep Iron Sky in cinemas for an extended period.
"We have enormous belief in the potential of the film to become a cult classic in the vein of Rocky Horror and The Room and keep audiences flocking to the Prince Charles for many years to come."
Vuorensola began work on the B-movie several years ago and quickly amassed a strong online following. Of the film's €7.5 million budget, around €1 million is crowd-sourced.
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Watch an exclusive clip from Iron Sky below: