Born in St. Laurence Pountney Hill in the City of London, he was the eldest son of the surveyor and architect Edward P. I'Anson (1775–1853).
[1] He was educated at the Merchant Taylors' School and at the College of Henri IV in France, and articled to his father at an early age.
I'Anson's son Edward Blakeway made funds available for the construction of the church, and many of his family are buried and memorialised in its churchyard.
There he made use of concrete for the internal works, an early example of this modern construction method that had previously only been used in experimental or minor projects.
[2] Those executed by him in the Italian style, such as the buildings of the British and Foreign Bible Society[1] at 146 Queen Victoria Street (1866–8)[6] were the most successful.
In many of his numerous duties as surveyor, and in some of his architectural works, notably the new Corn Exchange in Mark Lane, he was assisted by his eldest son, Edward Blakeway I'Anson.