April – 1842 general strike, a series of strikes and uprisings driven by Chartism and opposition to wage cuts and to the Corn Laws, breaks out, initially among Staffordshire coal miners, spreading to other industrial districts and continuing until September.[1]
4 June – in South Africa, hunter Dick King rides into the British military base in Grahamstown to warn that Boers have besieged Durban. He had set out eleven days earlier. The British Army dispatches a relief force.
16 July – Treason Act 1842 amends procedures and penalties against those threatening the monarch's life.[5]
August–October – First Anglo-Afghan War: British victory at the Battle of Kabul.
7–27 August – 1842 general strike: riots in and around Lancashire, spreading to Yorkshire by around 12 August. Because protestors remove plugs from textile mill boilers to prevent them working, these become known as the "Plug Plot Riots".[3][6]
9 August – the United States and United Kingdom sign the Webster-Ashburton Treaty agreeing the border between the United States and Canada.[7]
10 August – Mines and Collieries Act 1842 makes it illegal for women and girls of any age, and boys under ten years, to work underground, following the Children's Employment Commission (Mines) report produced in response to the 1838 Huskar Pit disaster (which resulted in the deaths by drowning of 26 children aged 7 to 17).
12–13 August – 1842 general strike: Preston Strike of 1842 and Lune Street Riot – 4 demonstrating cotton workers are shot dead by the military.[8]
Edwin Chadwick's critical Report on an inquiry into the Sanitary Condition of the Labouring Population of Great Britain published by the Poor Law Commission.[11]