She was a co-leader of the Green Party of England and Wales alongside Jonathan Bartley from 2018 to 2021, and was its sole leader from July to October 2021.

[6] She studied metallurgy and the science of materials at Trinity College, Oxford, graduating with a Master of Engineering (MEng) degree.

She became increasingly politically active, beginning a new career in an ethical temping agency that dealt with a wide range of charitable organisations.

[12] Berry was elected as the Green Party's female Principal Speaker unopposed in autumn 2006, succeeding Caroline Lucas MEP and, working alongside male Principal Speaker Derek Wall, served until autumn 2007, when Lucas resumed the post following an election.

She has advocated "green development" in Kings Cross Railwaylands (the largest brownfield site in the UK) to provide more family-housing.

[26] At the 2017 general election, Berry ran as the Green candidate for Holborn and St Pancras, which includes her Highgate ward.

She finished fourth, and the party lost its deposit in the seat, which was retained for Labour by Sir Keir Starmer.

[28] The same month, alongside celebrities and other public figures, Berry was a signatory to an open letter from Stylist magazine which called on the government to address what it described as an "epidemic of male violence" by funding an "ongoing, high-profile, expert-informed awareness campaign on men's violence against women and girls".

[32] Berry won a seat, but resigned three days later to hand it to Zoë Garbett, who had come fourth in the 2024 London mayoral election, for which she was criticised.

[40] On 20 October 2023, Berry stood down as a councillor in Camden to focus on her general election campaign in Brighton Pavilion.

[43] Berry is a co-sponsor of Kim Leadbeater's Terminally Ill Adults (End of Life) Bill on assisted suicide.

[44] Berry was a founder of the Alliance against Urban 4×4s, which began in Camden in 2003 and became a national campaign demanding measures to stop 4×4s (or sport utility vehicles) "taking over our cities".

The group was successful in getting the Mayor of London, Ken Livingstone, to adopt one of its founding principles when he introduced a higher congestion charge for vehicles with high emissions.

[49] In a 2021 video recorded for Humanists UK's 125th anniversary, Berry stated humanism was "an approach to life shaped by a rational, evidence-based understanding of our society and the problems we face – not only as individuals, but collectively" and rooted in "concern for other living beings, for our planet, and for future generations".