At the age of sixteen he became an apprentice to the surgeon John Taunton, assisting him in his clinical work and in the running of his anatomy school.

In 1808, when he was seventeen, he was among the group of young and intellectually curious apprentices who – at the instigation of John Tatum – formed the City Philosophical Society: Pettigrew gave an inaugural lecture on the subject of insanity.

Michael Faraday, another member, would later conduct chemical analyses for Pettigrew on minerals and other materials found inside mummies.

[4] Pettigrew played an active role in intellectual Georgian and Victorian society, corresponding regularly with many well known surgeons, physicians, scientists, writers and artists, such as John Coakley Lettsom, Astley Cooper, Michael Faraday, George Cruikshank and Charles Dickens.

[7] Another son, Samuel Thomas Pettigrew, became a chaplain in the East India Company and founded several key institutions in India, including Bishop Cotton Boys' School, Bishop Cotton Girls' School, St. Paul's Church, Bangalore, and All Saints' Church, Bangalore.