John Buchan, 1st Baron Tweedsmuir (1875-1940) was a Scottish novelist, historian and Unionist politician. After a brief legal career, Buchan simultaneously began his writing career and his political and diplomatic careers, serving as a private secretary to the colonial administrator of various colonies in southern Africa. He eventually wrote propaganda for the British war effort in WWI. In 1927 he was elected MP for the Combined Scottish Universities but spent most of his time on his writing career, notably writing The Thirty-Nine Steps and other adventure fiction. In 1935 he was appointed Governor General of Canada by King George V, on the recommendation of Prime Minister of Canada R. B. Bennett. He occupied the post until his death in 1940. He proved to be enthusiastic about literacy, as well as the evolution of Canadian culture, and he received a state funeral in Canada before his ashes were returned to the UK. I have only read his most famous novel. He was an active elder of St Columba's Church here in London for many years. It would be nice to check out some of the other titles - Prester John, Greenmantle. He wrote 30 novels as well as many other works.
Bonhoeffer uses a similar phrase 'worldly Christianity'. It's J Gresham Machen that I want to line up most closely with. See his Christianity and culture here. Having done commentaries on Proverbs (Heavenly Wisdom) and Song of Songs (Heavenly Love), a matching title for Ecclesiastes would be Heavenly Worldliness. For my stance on worldliness, see 3 posts here.