Short answers, pulled from the story.
The River Thames is 215 miles long, making it the longest river entirely in England and the second-longest in the United Kingdom after the River Severn. If measured from Seven Springs, a secondary source, the overall length reaches 229 miles.
The traditionally accepted source of the Thames is Thames Head in southern Gloucestershire, about 1.5 miles north of the village of Kemble. The river flows east and enters the North Sea near Tilbury in Essex and Gravesend in Kent via the Thames Estuary.
The Great Stink of 1858 was caused by the discharge of raw sewage, industrial waste, and animal offal into the Thames, which had worsened dramatically after the widespread installation of flush toilets in the 1850s. Pollution became so severe that sittings of the House of Commons at Westminster had to be abandoned, prompting engineer Joseph Bazalgette to build massive sewer systems along both embankments.
The Thames froze repeatedly during cold winters partly because the medieval London Bridge, with its many piers, slowed the tidal flow upstream. The first recorded Frost Fair was held in 1607. After a new London Bridge with fewer piers was built in 1825, the river flowed more freely and stopped freezing; the last Frost Fair had already taken place in 1814.
The Thames supports salmon, brown trout, short-snouted seahorses, tope and starry smooth-hound sharks, up to 700 grey and harbour seals, bottlenose dolphins, harbour porpoises, and a wide range of water birds including kingfisher, heron, great crested grebe and mute swan. Signal crayfish and Chinese mitten crabs are among the invasive species found in the river.
The Thames Tideway Scheme is a 25-kilometre tunnel constructed beneath the tidal Thames to capture sewage overflows before they enter the river, directing them to Beckton Sewage Treatment Works. It cost five billion pounds, was delayed by the COVID-19 pandemic, and was completed in February 2025. The project is projected to reduce sewage discharges into the Greater London stretch of the river by 90%.