When Dr Leo Pugh (Hugh Griffith) reminisces about his boyhood, he mentions "the village school in Marianglas". This is a village on the Isle of Anglesey (just off the north-west corner of Wales) and was Hugh Griffith's actual birthplace. The subtitles, though, replace Marian-glas with "Merioneth" which, although also in North Wales, is a county on the mainland.
The scenes in Winnerton Flats, especially the picnic by the family on the beach, are remarkably similar visually to scenes from John Ingram's 1952 documentary short, The Island, about the building of an oil refinery on the Isle of Grain.