This has been a year full of anniversaries, not all of them celebrated. In the history of the British Empire, 1759 was “the year of victories”, including Wolfe’s scaling of the heights of Quebec, with Pitt the Elder the strategic genius behind it. The British are now somewhat embarrassed by having had an empire, so there have been few celebrations of the 250th anniversary of that decisive year.

Yet 1759 is also remarkable in the annals of English literature. Tobias Smollett, himself a very readable novelist, was then proprietor and editor of The Critical Review, which he had founded. The April issue alone carries reviews of David Hume’s two quarto volumes of The History of England under the House of Tudor, and the catalogue of the Harleian collection of manuscripts, which had been purchased “by the authority of parliament for the use of the public”. The Harleian collection remains the cornerstone of the great manuscript collection of the British Library.

The catalogue itself has an introduction written by Samuel Johnson. The April Critical Review also has a review of Johnson’s only novel, The Prince of Abyssinia, a Tale, published by Dodsley at five shillings for two small volumes. The novel is generally referred to as Rasselas and is a reworking as a didactic narrative of ideas he had already expressed in his poem The Vanity of Human Wishes, and in his periodical essays in The Rambler and The Idler.

Even on its first appearance, the reviewer recognised that Rasselas, though it expresses important ideas, was by no means a “page turner”. The reviewer comments that: “No plot, incident, character, or contrivance is here used to beguile the imagination. The narrative might have been comprised in ten lines, all beside a flowery description of the happy valley, will please philosophers, but possibly be laid aside as unintelligible by the readers of novels.”

The reviewer nevertheless recommended Rasselas as “a beautiful epitome of practical ethics”. That is no longer what readers of novels are looking for, or indeed viewers of novels that have been adapted for television. It is inconceivable that anyone should produce a television version of Rasselas.

Even professed Johnsonians are quite likely never to have read Rasselas, by which omission they are missing a valuable piece of great literature. We know from Boswell’s Life, and from Johnson’s own letters, the circumstances in which Rasselas came to be written.

Johnson’s birth date was September 18, 1709; his 300th anniversary occurred last month. In January 1759 he was, therefore, in his 50th year. His mother was still living in Lichfield, where Johnson had been born and raised. Johnson was an esteemed London author, but short of money; what money he had he used to help his mother, who was 90. On January 13 he already knew that she was seriously ill. He wrote in his letter to her: “The account which Miss Porter [his stepdaughter] gives me of your health pierces my heart.”

To accompany that letter, Johnson had got together 12 guineas to send his mother, six of which he had borrowed from Mr Allen, the printer. On January 20 Johnson wrote his last letter to his mother: “Dear honoured mother, neither your condition nor your character make it fit for me to say much. You have been the best mother, and I believe the best woman in the world. I thank you for your indulgence to me and beg forgiveness for all that I have done ill, and that I have omitted to do well. God grant you his Holy Spirit and receive you to everlasting happiness, for Jesus Christ’s sake. Amen. Lord Jesus receive your spirit. Amen, I am, dear mother, your dutiful son, Sam Johnson.”

Old Mrs Johnson died either on the 20th or 21st and was buried in Lichfield on January 23.

Samuel Johnson wrote Rasselas in the evenings of a single week and sold it to the booksellers for £100; they gave him another £25 for the second edition. All these sums need to be multiplied by about 50 to obtain 21st century values. Rasselas earned Johnson the equivalent of £6,250, enough to pay for Mrs Johnson’s funeral expenses and her small debts.

Through studies of Johnson’s relationship with Mrs Thrale, who later wrote his life, we are more aware than we used to be, of the depth of Johnson’s fear of insanity. Like George III he may have been padlocked as a medical treatment for his mental condition. Rasselas was written in a period of intense reaction following the loss of his mother, and it expresses his anxieties. “Disorders of intellect happen much more often than superficial observers will easily believe. Perhaps if we speak with rigorous exactness, no human mind is in its right state.”

In Rasselas, Johnson emphasises the limitations of all human life. Perhaps the only sentence in Rasselas that is still well remembered is his comment on matrimony: “Marriage has many pains, but celibacy has no pleasures.”

We think of Johnson as an English Tory, which he was, but the basis of his beliefs was that he was a Christian and led a life of prayer. Important as Rasselas is as an expression of his ethical philosophy, his Prayers and Meditations is even more important as an indication of his spiritual life. On the day his mother was buried he prayed for her in words which give some idea of his belief in the humility of prayer: “I am sorrowful, O Lord. Let not my sorrow be without fruit.”

Times Recommends

• Britain doesn’t need a dose of shock therapy
• Why the sea eagle has no right to land here
• Let older women have a voice at the BBC