Short answers, pulled from the story.
The Anglian ice sheet changed the course of the River Thames about 450,000 years ago. This event diverted the river onto its present path through Greater London after floodwaters burst from large ice lakes in Hertfordshire.
The name River Thames derives from the Brittonic word Tamesas which appears in Latin records as Tamesis. Early variants include Tamis and Temes in Old English while some scholars suggest the root element meant dark or muddiness.
Julius Caesar encountered the River Thames during his second expedition to Britain in 54 BC when it presented a major obstacle. The Romans later built fortifications along the valley including a camp at Dorchester starting in AD 43 under Emperor Claudius.
Pollution reached such an extreme during the Great Stink of 1858 that sittings of the House of Commons had to be abandoned. Gasworks alongside the river leaked spent lime ammonia cyanide and carbolic acid into the water creating unnaturally warm temperatures.
An early flood control device called the Thames Barrier opened in the early 1980s to protect London from storm surges. The barrier closes to tides several times a year preventing damage to low-lying areas upstream as demonstrated by the severe 1928 Thames flood.