Wall teaches economics at Duff Miller - a private sixth form college. He is also a visiting tutor at the Department of Politics at Goldsmiths College, University of London, where he teaches a course on the new radical political economy. His PhD thesis was titled The Politics of Earth First! UK.

He has written a series of books on eco-socialism and green politics. Getting There: Steps Towards a Green Society was published in 1990, and looked at the strategies of green politics. A Green Manifesto for the 1990s, also written in 1990, outlined the Green vision. In 1994, a book examining the roots of ecological politics, Green History: A Reader in Environmental Literature, Philosophy, and Politics, was released. Also during 1994, he released Weaving a Bower Against Endless Night: An Illustrated History of the Green Party as a Green Party publication. Having taken a BSc in Archaeology at the University of London, he subsequently completed a PhD at the University of the West of England, later published in revised in 1999 as a book entitled Earth First! and the Anti-Roads Movement: Radical Environmentalism and Comparative Social Movements. Academic reviews for the book were mixed. One academic reviewer commented that the book offered ‘valuable and often original information about the radical environmentalist movement’ but ‘fails to provide a systematic analysis of the topic’ and uncritically paid little attention to possible personal agendas of the activists interviewed.

His most recent work, Babylon and Beyond: The Economics of Anti-Capitalist, Anti-Globalist and Radical Green Movements, looks at the history of anti-capitalism, including reformist capitalists (such as Joseph Stiglitz), anti-corporate critics (namely Naomi Klein and David Korten), monetary reformers, eco-socialists (especially Joel Kovel), Marxists, green localists (including Caroline Lucas, Mike Woodin and Vandana Shiva) and anarchists (particularly Michael Hardt and Toni Negri). It includes a foreword by Nandor Tanczos, the Green Party of Aotearoa New Zealand MP.

Wall is an associate editor of the left-wing magazine Red Pepper and an advisory editor of Socialist Resistance. He has also published articles in academic journals such as Environmental Politics, Social Movement Studies and Capitalism Nature Socialism.

Wall first became involved in the Green movement in 1979. He joined the Ecology Party (later the Green Party of England and Wales) in 1980. By 1987, Wall was standing for the Ecology Party against Chris Patten in Bath. At the time of the European Parliament election in 1989, Wall was one of three National Speakers in the Green Party. In the elections themselves, which saw the Green Party gain over 2 million votes (14.5% of the national poll), Wall received 15% of the vote in the Bristol constituency. During his time in the Green Party, Wall has been a Parish Councillor.

Wall rose to national prominence in the wake of the 1989 result, when he presented himself to the national press as a 'left wing' candidate for the ruling Green Party Council in opposition to the leadership. He styled himelf a 'maverick' and a Green 'fundamentalist'. He was then in turn attacked as a 'parasite' in a series of individualized attacks by pragmatists such as Sara Parkin and Jonathon Porritt.. These divisions contributed to highly negative press coverage at the time.

Wall was also a prominent figure opposing the organisational changes by the group known as Green 2000 along with Penny Kemp and John Norris.. Organising a faction within the Green Party known as the Association of Socialist Greens, this left grouping was accused by pragmatists such as Mallen Baker as being responsible for ensuring the party was "going knowhere fast".

At the 2005 general election, Wall stood as a candidate for Windsor and received 2.5% of the votes. In November 2005, he was beaten by Keith Taylor in the election to be the Male Principal Speaker of the Green Party, by 851 votes to 803.

He is a founder member of the Green Left, an anti-capitalist and eco-socialist faction within the Green Party, which held its first meeting in June 2006.

Wall has continued to be an out-spoken member of the Green Party, particularly on the issue of entering into alliances with other parties. He was given a vote of censure by the Green Party Association of Green Councillors (AGC) when he made comments concerning the alliance between Green Party, Conservative and Liberal Democrat councillors on the Leeds City Council; he stated in Red Pepper magazine that, "While I understand that repellent Labour councils may be the only substitute for alliances with Liberal Democrats and Conservatives, the fall in our Leeds West vote suggests that voters were displeased by a perceived shift to the right by Yorkshire Greens".