In the late 1880s athletics experienced its first boom. The established clubs of the time, south of the River Thames, were Ranelagh Harriers, Thames Hare & Hounds, South London Harriers and Blackheath Harriers. These clubs were extremely careful in accepting new members and this led to many further clubs being formed. Often these newer, minor, clubs were attached to Public Houses. Their fortunes were very mixed: some continued but many died, amalgamated, or were absorbed by others. The standing of the established clubs seemed unaffected by the boom. The newer, clubs accepted the 'Junior' or 'Second-Class' status put upon them by the established clubs and they had no opportunity of competing against them.

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In November 1887 a group of the newer clubs from South London, led by Reindeer Harriers, asked the Southern Counties Cross Country Association for permission to run a South of the Thames Second Class Inter-Club Race. Similar clubs North of the Thames requested that the race be extended to include them but this was turned down by the South of Thames clubs and so the North of the Thames clubs formed their own association.

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On 14th January 1888 the first South of the Thames Second Class Inter-Club Race took place on Wandsworth Common and the venue continued to be used up to and including 1894.  A formal constitution was written in 1893 but the true start of the Association was, without question, 14th January 1888.

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In time the Association expanded from a South London Association to a truly South of the Thames Association with clubs from Surrey, Kent, Sussex, Wiltshire, Berkshire and Hampshire (including the Channel Islands). Subsequently, the 'established' clubs all, over the years, affiliated to the Association and have very often hosted its races.

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In 1910 the Association started the annual 'Junior' (by standard) races in addition to the Championship race. Initially the 'Junior' races were on a County, or group of Counties, basis but changed to one race only in 1933. The 'County idea continued, however, with the 'County' Medals given at these races.

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In the recent past the Association has celebrated 100 years since the first Championship Race and also the 100th Championship Race. Both were followed by Suppers at Blackheath Harriers' headquarters and attended by many previous winners, including (on the occasion of the 100th race) the 1938 winner.

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At one time barring clauses prohibited winning team members from returning to the competition in following years while those who placed highly in the National Cross Country Championships were also not allowed to take part. Around the turn of the millennium these restrictions were dropped. The 'Junior' race became known as the 5 miles Team Race at this time.  A women's Team race was introduced in 2001 and three years later women were welcomed into the Championship race, held over about 7.5 miles.  

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The fixture list is generally very much fuller now than in earlier days but the Committee still feel the Association has a part to play - especially for the 'club' runner.