In July 1872, one of the most curious articles in the history of British journalism appeared in the much respected Contemporary Review. The anonymous essay, entitled ‘The “Prayer for the Sick” – hints towards a serious attempt to estimate its value’, challenged the Christians of the nation to conduct an experiment to determine the physical efficacy of prayer. A letter from physicist John Tyndall of the Royal Institution introduced the proposal, the author of which was later identified as Henry Thompson, an eminent London surgeon.

Thompson admitted that few prayers were actually open to scientific or quantitative investigation. The prayers for the sick in the Book of Common Prayer were, however, an exception and appeared to constitute a set of petitions ‘from a study of which the absolute calculable value of prayer … can almost certainly be ascertained’. These fell into two categories – general prayers said every Sunday and specific prayers offered for particular individuals. Although Thompson desired no one to be deprived of the benefits afforded by general prayers, he did propose that