Grill grew up in a rural areaHampshire<ref>{{Cite web|url=https://www.caughtbytheriver.net/2017/07/ernest-seton-graphic-novel-conservationwilliam-grill-the-wolves-of-currampaw/|title=The Wolves of Currumpaw|website=Caught by the River|date=14 July 2017|accessdate=17 April 2024}}</ref> and worked on a farm as a young adult, experiences which have influenced his art and writing.<ref name=":0" /> He graduated from [[University College Falmouth]], is dyslexic, and runs a weekly art club at a local school.<ref>{{cite news |last=Daniel |first=Lucy |date=2015-06-27 |title=Why a picture book about Ernest Shackleton marks a publishing revolution |newspaper=The Telegraph |url=https://www.telegraph.co.uk/books/authors/why-a-picture-book-about-ernest-shackleton-marks-a-publishing-re/ |access-date=2016-09-08 |archive-date=7 July 2017 |archive-url=https://web.archive.org/web/20170707135450/http://www.telegraph.co.uk/books/authors/why-a-picture-book-about-ernest-shackleton-marks-a-publishing-re/ |url-status=live }}</ref><ref>{{cite news |author=<!--Staff writer(s); no by-line.--> |date=2015-06-15 |title=True historical stories inspire Carnegie and Greenaway winners |newspaper=BBC News |url=https://www.bbc.co.uk/news/entertainment-arts-33226279 |access-date=2016-09-08 |archive-date=18 November 2016 |archive-url=https://web.archive.org/web/20161118020037/http://www.bbc.co.uk/news/entertainment-arts-33226279 |url-status=live }}</ref>
