Fletcher trained as a barrister, entering the Middle Temple in 1838 and being called to the bar in 1841.
[2] From a young age, Fletcher wrote reports on social and health issues.
[2] In 1850 Fletcher published a Summary of the Moral Statistics of England and Wales; and in the following year a work on Education: National, Voluntary, and Free.
[2] He was unconvinced of the moral superiority of communities that were relatively sparsely developed, such as small towns and farming areas, presaging views later held by Herbert Spencer and Norbert Elias.
He was member of the council of the British Association, and acted as secretary to its statistical section.