Agnew was born in Dundonald and studied at Brooklands Primary School, Grosvenor Grammar School and Queen"s University Belfast. He grew up around a "very negative political landscape", where politics was "about being anti-Catholic, anti the Pope and anti-Sinn Fein".
Queen"s University Belfast.
He was elected as an Modern Language Association to the Northern Ireland Assembly in May 2011. Agnew was a vegan from the age of 19 to 30, and is now a vegetarian. He has appeared as a singer for a local band called The Killing Spree.
Agnew joined the Green Party in 2003 during its campaign against the invasion of Iraq.
During a protest march from Queen"s to the United States Consulate, he met John Barry, who convinced him that "the Green Party had a practical agenda of what needed to be changed". He came to believe "environmental justice is interlinked" with social justice.
At the Northern Ireland Assembly election, 2007, he stood in Belfast East, where he took 2.2% of the vote and was not elected. He was the party"s candidate for the European Parliament election, 2009, where he increased the party"s share to 3.3%, although he still came bottom of the poll.
At the 2010 United Kingdom general election, he stood in North Down, taking 3.1% of the votes cast.
In January 2011, Agnew was elected as the first leader of the Green Party, beating Cadogan Enright in a postal ballot. He successfully contested the North Down seat in the Northern Ireland Assembly election, 2011.
Brian Wilson was successful for the party at the election, and Agnew became his full-time research officer
4th Northern Ireland Assembly.
