Born into a mill-owning family in the textile town of Barmen in Germany in 1820, Engels (whose picture on this page was taken as early as 1845) had already earned a reputation as a radical journalist before his father - worried by his politics - despatched him to England in 1842 to look after the family's business interests and stay out of trouble.
By day, Engels was a diligent businessman, representing his father at the Victoria Mill of Ermen and Engels at Weaste, in Salford.
But by night he became a social investigator, prowling the mean, dangerous streets of Manchester's slum areas gathering material for what was to become his classic book, The Condition of the Working Class in England.
His first stay in the city lasted only two years, but that was long enough for him to gather a mass of information on the appalling situation of Manchester's poor slum dwellers.
In 1844, he returned home to finish his book. The volume was published in Germany in 1845 but was not made available in an English translation until 47 years later, by which time it might have been expected to have lost much of its impact.
However, its simple but colourful style and straightforward language made it into a lasting work of historical importance.
The book was a damning indictment of social attitudes of the 1830s and 40s, pointing up the horrors of back-to-back housing, cellar dwellings and poor sanitation.
Substantial extracts from the The Condition of the Working Class in England can be found elsewhere on this site.
Meanwhile, Engels returned to the Continent, joining Marx and other German revolutionaries in Brussels.
He took part in the German uprisings of 1848, before returning to Manchester in 1850 where he again took charge of his father's business, operating both at Weaste and in the company's office at No 7, Southgate, which is now the rear of Kendal's Deansgate store.
In his later years, Engels devoted much of his time and money to subsidising Marx, who was in London writing Das Kapital. He died in 1895.