Patronised by leaders of society of doubtful reputation, Allen apparently obtained a livelihood for some time by pandering in the press to the fashionable vices of the age.
His first work, a 'Poem inscribed to his Britannic Majesty,’ published in 1761, shortly after the accession of George III of Great Britain, is unobjectionable; but circa 1768 he is generally credited with aiding the son of the Marquis of Granby to defend Lord Baltimore, who was awaiting his trial in Newgate on a charge of rape, by the publication of an anonymous pamphlet entitled 'Modern Chastity; or the Agreeable Rape, a poem by a young gentleman of sixteen in vindication of the Right Hon.
'The present Lord Granby (who had succeeded to the title in 1770),’ he writes, 'is an author, and has written a poem on "Charity" (i.e. a probable misreading for 'Chastity'), and in prose a "Modest Apology for Adultery".
An arranged change of rectorships allowed Allen to obtain the living of St. Anne's parish in Annapolis, and he became the chaplain for and a drinking buddy of Governor Horatio Sharpe.
[2] Allen gave up the position at St. Anne's (but not St. James) when he secured the most lucrative parish in the colony, All Saints Church in Frederick, Maryland (worth £1000 sterling annually), after the early death of the scholarly incumbent, Rev.
Allen technically served for seven years until the American Revolutionary War, but the vestry locked him out of the church almost immediately after learning of the ongoing St. James situation, causing him to flee to Philadelphia and hire a curate long before he fled back to England.
After a trial, which attracted general public attention, Allen, in spite of his plea for benefit of clergy and the evidence as to his character adduced by Lords Bateman, Mountnorris, and many fashionable ladies, was convicted of manslaughter (but Morris acquitted), and sentenced to a fine of one shilling and six months' imprisonment.