After losing his lectureship in comparative anatomy at the London Hospital in June 1881 (ODNB), Aveling continued to teach in the Hall of Science school he had begun in 1879 on behalf of the National Secular Society; his science classes were given at his own ‘Practical Science Laboratory’ at 13 Newman Street (Royle ed. 1976, p. 120; Royle 1980, pp. 317–18).

The visit took place on Wednesday 28 September; after a family lunch, CD, Francis Darwin, Aveling, and Büchner retired to smoke in CD’s study when, as Aveling later reported in a pamphlet on CD’s religious views, the conversation turned to religion (Aveling 1883). Büchner also later recalled that CD defended his position as an agnostic ‘with some warmth’ in opposition to Aveling and Büchner’s atheistical views (Büchner 1901, p. 147). Büchner had been involved in controversies over materialism and anticlericalism in Germany; Aveling had published English translations of his work (see Correspondence vol. 28, letter from E. B. Aveling, 12 October 1880). The visit confirmed Emma Darwin’s worst fears; in a letter to George Howard Darwin on 28 October 1881 she had stated, ‘Herr Büchner is coming today to luncheon—& let us hope that he talks English & will refrain from airing his very strong religious opinions—’ (DAR 210.3: 22). The other visitors at lunch were house guests, Camilla Pattrick and her husband, Reginald Saint Pattrick, vicar of Sellinge, Kent, who, according to Emma Darwin, was interested in science, but ‘so languid’ that he was ‘hard work’ (ibid.).