- 4 July
- 1829 – George Shillibeer's first London Omnibus begins operating between the Yorkshire Stingo, Paddington and the Bank of England in the City of London.
- 1904 – Metropolitan Railway extends from Harrow-on-the-Hill to Uxbridge.
- 1932 – Piccadilly line extends from Hammersmith to South Harrow.
- 1936 – Metropolitan line ends services between Quainton Road and Verney Junction.
- 1948 – A mid-air collision above Northwood between a Scandinavian Airlines passenger plane and an RAF transport plan kills 39.