WATCH: Our full coverage of Greta Thunberg in Bristol.
Climate change campaigner Greta Thunberg has been taking part in The Bristol Youth Strike 4 Climate.
The Swedish teenager and activist was the headline speaker at the event on College Green.
Police said there were more than 20,000 in the crowd, although organisers said they estimated the figure to be closer to 30,000.
WATCH: ITV West Country reporter Robert Murphy meets Greta as she arrives at Bristol Temple Meads station.
Who? What? Where?
The 17-year-old delivered a speech on College Green outside City Hall at 11:45am.
She took aim at officials and governments but also praised climate activists in the city for halting the expansion of Bristol Airport.
She told the crowds gathered in the rain: "We will not be silenced because we are the change, and change is coming whether you like it or not."
The Swedish teenager went on to join protesters, including school pupils, on a march through the city centre accompanied by a Samba band.
Road closures will be in place between 9am and 5pm (including affected bus stops):
Lower Maudlin Street from its junction with Whitson Street to Lewins Mead
Victoria Street from Bristol Bridge to its junction with Counterslip
St Augustine’s Parade
Anchor Road from St Augustine’s Parade to Cannons Way
St Georges Road from Park Street to its junction with Frog Lane
Deanery Road from its junction with St Georges Road to the site of College Green
In a letter to parents and supervisors of those attending the demonstration, Avon and Somerset Police warned there will be "major disruption to the city."
What's the weather going to be like?
The current forecast predicts rain and strong winds, with temperatures reaching 12 °C, and there's a Met Office warning in force for that wet weather.
Click here for updates.
Will she visit her giant mural?
It's been confirmed that Ms Thunberg will not visit the giant mural of herself, which was painted in 2019 by Bristol artist Jody Thomas.
She is aware of the creation - which is on the side of the Tobacco Factory - and even made the image her profile picture on social media at the time.
Former Mayor and owner of the Tobacco Factory, George Ferguson, tweeted this morning that she would not be visiting Bedminster.
Why is she coming?
Ms Thunberg founded the youth strike movement in 2018 after she sat in solitude outside the Swedish Parliament building.
Since then she has inspired millions of students across the world to participate in strikes held in cities such as London, Paris and Madrid - as well as here in the West Country.
Who else will be there?
Joining Ms Thunberg on stage at the climate demonstration will be 17-year-old Mya-Rose Craig from Somerset.
She received it from Bristol University, for using her platform as a world-leading ornithologist to promote greater diversity in the wildlife andconservation sectors.
Will her parents be joining her?
The world-renowned activist was last in the West Country in September 2019 when she set sail from Plymouth to attend a UN meeting in New York.
Her actor father, Svante, joined her for the expedition as she crossed the Atlantic for the UN Action Climate summit.
Her mother Malena Ernman - an opera singer and former Eurovision Song Contest participant - has also supported her daughter, but it's unknown whether either will be in Bristol with Greta on Friday.