I was one of the schoolchildren who ran on in the closing minutes of the film, to the farm at the foot of Worsaw Hill in Lancashire. There were several takes of this scene, and we alternately ran into the farmyard from along the stream in front, and down a rather steep part of the hill and into the farmyard. Many of the children chosen for disciple parts and principal parts were from Chatburn Primary School. The entire front row in the final gate scene were also Chatburn schoolkids. We were paid ten shillings as extras for each day's shooting. I remember earlier in the year - probably 1960 - Bryan Forbes and Dickie Attenborough came round to the school, and we were all lined up against a wall while they were doing cast selections.
Of course the film was a big hit locally when it premiered (at the Odeon in Burnley). It still is, as most people in the surrounding villages are related to someone who was in it.
It was a long time before I was able to develop a proper adult opinion of 'Whistle'. What strikes me now is how opinion in various reviews I have seen, and discussed, splits along the lines of the division of opinion among the protagonists. Having once 'identified' The Man as Jesus, even in spite of ("adult") evidence to the contrary, Kathy and Nan, and apparently also the disciples, persist in believing that he was Jesus and is being persecuted all over again. Charlie is the lone dissenter, who interprets the evidence of his senses and concludes "It's not Jesus. It's just a fella". So the overall flavour of the film from an analytical perspective is that in the matter of religious faith, presentation of contrary facts is completely irrelevant to the persistence of the belief. A more cynical twist on this: in so far as only children were party to the belief, while adults only saw a dangerous criminal, it suggests that irrational belief systems require a childlike worldview. This is doubly damning for Faith versus Facts.
And yet, People Still Believe.