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More than 5000 entries on the history, culture and life of Britain (published in 1993 by Macmillan, now out of print)
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Thames
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The longest river wholly in England (and some would say in Britain, see the *Severn). Its length is usually given as about 338km/210m from the Cotswolds to the Nore, the point where its estuary is joined by the Medway. There are two candidates for its source: the traditional one is Thames Head (5km/3m SW of Cirencester); the other, adding about 8km/5m to the overall length, is the source of a tributary, the Churn, at Seven Springs (6km/4m S of Cheltenham). The Thames links some of the most historic of English towns, castles and palaces: Oxford (where it is called the *Isis), *Windsor, *Hampton Court, *London (with the Houses of Parliament and the Tower on its bank) and *Greenwich.
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*London Bridge has been historically the lowest point at which the river could be crossed. In the late 19C *Tower Bridge was built a few hundred yards downstream; and many miles further down the river the Queen Elizabeth Bridge at Dartford, connecting with the M25, was opened in 1991. The first tunnel under the Thames was begun by *Brunel's father in the 1820s and was completed in 1843. There are road tunnels at Rotherhithe (1908), at Blackwall (two of them, 1897 and 1967) and at Dartford (again two, 1963 and 1980). For about 16km/10m downstream from Tower Bridge the estuary was developed in the 19C as a series of extremely busy docks; it is now being redeveloped as *Docklands.
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The river is tidal throughout London (as far upstream as Teddington) and the capital city was in regular danger of flooding until the completion in 1982 of the Thames Barrier at *Woolwich. The barrier, crossing the river where it is about 520m/569yds wide, consists above water level of a series of narrow islands supporting hydraulic machinery (in casings with a profile reminiscent of the Sydney Opera House). The machines control vast steel gates, which normally rest in concrete cavities on the river bed so that ships can pass above them; if the gates need to be raised against an unusually high tide (a precaution which happens on average about once a year), they rotate upwards to form a solid vertical wall. A routine exercise of closing the barrier for a full day is also carried out once a year – an event announced well in advance and something of a tourist attraction.
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