| Date | Protest | Cause | Organisers | Location | Attendance |
| Organisers' estimate | Police estimate | Third-party estimates |
| 15 February 2003 | Stop the War | Iraq War | Stop the War Coalition (StWC) | London | 1,500,000 | 750,000 | "around a million" |
| 23 March 2019 | Put it to the People march | Second EU referendum | People's Vote, European Movement UK, Open Britain | London | 1,000,000 | | 312,000 to 400,000 |
| 19 October 2019 | Let Us Be Heard | Second EU referendum | People's Vote, European Movement UK, Open Britain | London | 1,000,000 | | 105,000 to 216,000 |
| 11 November 2023 | PSC March for Palestine | Gaza war | Palestine Solidarity Campaign (PSC) | London | 800,000 | 300,000 | |
| 20 October 2018 | People's Vote march | Second EU referendum | People's Vote, European Movement UK, Open Britain | London | 700,000 | 250,000 | 450,000 |
| 11 October 2025 | PSC March for Palestine | Gaza war | Palestine Solidarity Campaign (PSC) | London | 600,000 | | |
| 26 March 2011 | March for the Alternative | Austerity | Trades Union Congress (TUC) | London | 500,000 | 250,000 (more than) | |
| 13 September 2025 | Unite the Kingdom | Anti-immigration | Tommy Robinson | London | | 110,000 | up to 150,000, 56,000-76,000[better source needed] |
| 28 October 2023 | PSC March for Palestine | Gaza war | Palestine Solidarity Campaign | London | | 50,000 to 70,000 | |
| 22 March 2003 | Stop the War | Iraq War | Stop the War Coalition, Campaign for Nuclear Disarmament (CND) | London | 500,000 (StWC), 200,000-300,000 (CND) | 200,000 | |
| 23 September 2002 | Liberty & Livelihood | Hunting and countryside causes | Countryside Alliance | London | 407,791 | 400,000 | |
| 22 October 1983 | CND march for peace | Nuclear weapons | Campaign for Nuclear Disarmament | London | 400,000 | 200,000 | |
| 24 September 2002 | Stop the War | Iraq War | Stop the War Coalition, Muslim Association of Britain (MAB) | London | 400,000 | 150,000 | |
| 21 October 2023 | PSC March for Palestine | Gaza war | Palestine Solidarity Campaign | London | | 100,000 | |
| 25 November 2023 | PSC March for Palestine | Gaza war | Palestine Solidarity Campaign | London | | 45,000 | |
| 17 February 2024 | PSC March for Palestine | Gaza war | Palestine Solidarity Campaign | London | | 30,000 | |
| 24 October 1981 | CND march for peace | Nuclear weapons | Campaign for Nuclear Disarmament | London | 250,000 | | |
| 13 July 2018 | Stop Trump | Trump's visit to the UK | Various | London | 250,000 | | |
| 2 July 2005 | Make Poverty History | Raise awareness of global poverty | Various, coordinated by British Overseas NGOs for Development (bond) | Edinburgh | 225,000 | 225,000 | 225,000 |
| 23 November 1985 | Ulster Says No | Anglo-Irish Agreement | Democratic Unionist Party, Ulster Unionist Party | Belfast | 203,000 | | 100,000 |
| 18 November 2003 | George W. Bush's state visit to the UK | George W. Bush's Foreign Policy (Bush Doctrine) | Stop the War Coalition, Campaign for Nuclear Disarmament,Muslim Association of Britain | London | 200,000 | 100,000 | |
| 3 February 2024 | PSC March for Palestine | Gaza war | Palestine Solidarity Campaign | London | | 20,000 | |
| 30 March 2024 | PSC March for Palestine | Gaza war | Palestine Solidarity Campaign | London | 200,000 | | |
| 31 March 1990 | 1990 Poll tax protest | Poll tax | All Britain Anti-Poll Tax Federation | London | 200,000 | | |
| 22 May 2021 | PSC March for Palestine | 2021 Israel–Palestine crisis | Palestine Solidarity Campaign | London | 180,000 | | |
| 26 March 2022 | UK with Ukraine | Russian invasion of Ukraine | European Movement UK, Mayor of London | London | | | "tens of thousands" |
| 1 April 1961 | Aldermaston Marches | Nuclear weapons | Campaign for Nuclear Disarmament | London to Berkshire | 150,000[citation needed] | | |
| 31 January 2009 | 2009 BTF protest | Tamil genocide Sri Lanka's genocide of Tamils | British Tamils Forum | London | 150,000 | 50,000 | |
| 26 November 2023 | March Against Antisemitism | Rise in antisemitism | Campaign Against Antisemitism | London | 100,000 | 50,000 | |
| 9 December 2023 | PSC March for Palestine | Gaza war | Palestine Solidarity Campaign | London | | 40,000 | |
| 17 March 1968 | Grosvenor Square peace march | Vietnam War | Vietnam Solidarity Campaign | London | 100,000 | 20,000[better source needed] | 10,000 |
| 18 November 2001 | Stop the war | Afghanistan War | Stop the War Coalition | London | 100,000 | 15,000 | |
| 6 November 2021 | COP26 Nature Day march & rally | Climate change | COP26 Coalition | Glasgow | 100,000 | | |
| 19 September 2019 | September 2019 Youth Climate Strikes | Climate change | UK Student Climate Network | London | 100,000 | | |
| 23 June 2018 | People's Vote March | Second EU referendum | People's Vote, European Movement UK, Open Britain | London | 100,000 | | |
| 26 July 2025 | Trans Pride | Trans rights | London Trans+ Pride | London | 100,000 | | |
| 18 March 2006 | Stop British involvement in the Iraq War | Iraq War | Stop the War Coalition, Campaign for Nuclear Disarmament,Muslim Association of Britain | London | 80,000-100,000 | 15,000 | |
| 15 February 2003 | Stop the War | Iraq War | Stop the War Coalition | Glasgow | 80,000 (more than) | 30,000 | 100,000 |
| 4 June 2019 | Stop Trump | Trump's State Visit to the UK | Stop Trump coalition | London | 75,000 | | |
| 28 March 1959 | Aldermaston march | Nuclear weapons | Campaign for Nuclear Disarmament | London to Berkshire | 60,000[citation needed] | | |
| 10 November 2010 | Fund Our Future: Stop Education Cuts | Education cuts | National Union of Students | London | 52,000 | | |
| 28 March 2009 | March for Jobs, Justice & Climate | 2009 G20 London summit | Put People First | London | 35,000 | 35,000 | |
| 28 February 2020 | Climate Strike | Climate change | Bristol Youth Strike 4 Climate | Bristol | 30,000 | 15,000 | |
| 16 May 1832 | Meeting of the Unions | Suffrage | Birmingham Political Union | Birmingham | | | 200,000 |
| 4 October 1936 | Battle of Cable Street | Anti-fascist response to the British Union of Fascists march. | Various anti-fascist groups: Communists (Communist Party of Great Britain),Socialists, Trade unionists, Anarchists, British Jews, Independent Labour Party | London | | | 100,000-310,000 |
| 16 August 1819 | Gathering at Peterloo (leads to the Peterloo Massacre) | Reform parliamentary representation | Manchester Patriotic Union | Manchester | | | 60,000 |
| 10 January 2009 | Ceasefire in Gaza | Gaza War (2008–2009) | Stop the War Coalition, British Muslim Initiative, Palestine Solidarity Campaign | London | | 20,000 | 50,000 |
