A half marathon is a road running event of 21.0975 km (13 mi 192½ yd)—half the distance of a marathon.

It is common for a half marathon event to be held concurrently with a marathon, using almost the same course with a late start, an early finish or shortcuts.

If finisher medals are awarded, the medal or ribbon may differ from those for the full marathon.

The half marathon is also known as a 21K, 21.1K or 13.1 miles, although these values are rounded and not formally correct.

The 10K run is a long-distance road running competition over a distance of.

Also referred to as the 10K road race, 10 km, or simply 10K, it is one of the most common types of road running event, alongside the shorter 5K and longer half marathon and marathon.

It is usually distinguished from the 10,000 metres track running event by stating the distance in kilometres, rather than metres.

The marathon is a long-distance race, completed by running, walking, or a run/walk strategy.

There are also wheelchair divisions.

The marathon has an official distance of 42.195 kilometres (26.219 miles; 26 miles 385 yards), usually run as a road race.

The event was instituted in commemoration of the fabled run of the Greek soldier Pheidippides, a messenger from the Battle of Marathon to Athens, who reported the victory.

London is the capital and most populous city of England and the United Kingdom.

Standing on the River Thames in the south east of the island of Great Britain, London has been a major settlement for two millennia.

It was founded by the Romans, who named it Londinium.

London's ancient core, the City of London, largely retains its medieval boundaries.

Since at least the 19th century, "London" has also referred to the metropolis around this core, historically split between Middlesex, Essex, Surrey, Kent and Hertfordshire, which today largely makes up Greater London, a region governed by the Mayor of London and the London Assembly.

Running is a method of terrestrial locomotion allowing humans and other animals to move rapidly on foot.

Running is a type of gait characterized by an aerial phase in which all feet are above the ground (though there are exceptions).

This is in contrast to walking, where one foot is always in contact with the ground, the legs are kept mostly straight and the center of gravity vaults over the stance leg or legs in an inverted pendulum fashion.

A characteristic feature of a running body from the viewpoint of spring-mass mechanics is that changes in kinetic and potential energy within a stride occur simultaneously, with energy storage accomplished by springy tendons and passive muscle elasticity.

The term running can refer to any of a variety of speeds ranging from jogging to sprinting.