The London Marathon is an annual marathon held in London, United Kingdom. Founded by athletes Chris Brasher and John Disley in 1981, it was typically held in April but has now moved to October. The course is set around the River Thames, starting in Blackheath and finishing at The Mall. The marathon is run over a largely flat course around the River Thames, and spans 42.195 kilometres (26.219 mi).

The course begins at three separate points: the 'red start' in southern Greenwich Park on Charlton Way, the 'green start' in St John's Park, and the 'blue start' on Shooter's Hill Road. From these points around Blackheath at 35 m (115 ft) above sea level, south of the River Thames, the route heads east through Charlton. The three courses converge after 4.5 km (2.8 miles) in Woolwich, close to the Royal Artillery Barracks.

As the runners reach the 10 km mark (6.2-mile), they pass by the Old Royal Naval College and then head towards the 'Cutty Sark' (British clipper ship) drydocked in Greenwich. Heading next into Deptford and Surrey Quays/Rotherhithe in the Docklands, and out towards Bermondsey, competitors race along Jamaica Road before reaching the half-way point as they cross Tower Bridge. Running east again along The Highway through Wapping, competitors head up towards Limehouse and into Mudchute in the Isle of Dogs via Westferry Road, before heading into Canary Wharf.

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