London Welsh Football Club are one of the oldest in London having played its first competitive match on 18 October 1891, although it had been founded around a year earlier by officers of the Welsh regiments, with the aim to "honourably uphold the reputation of Wales in the Metropolis".
Their first season was a difficult one, including an emphatical 0–12 loss to Millwall Athletic in the 1891–92 season. They played in the London League in the 1896–97 season, in which they finished 7th of seven. They were suspended towards the end of the season, and the points from their two remaining games went to their opponents, Thames Ironworks (Who later changed their name to West Ham), who as a result finished second. Another noteworthy fixtures in the early days were a 1:0 defeat and 1:1 draw against Tottenham Hotspur in 1894. At this time the Club had 90 members who were all, exclusively, Welsh.
The team was soon to be nicknamed "Preston North End" because "they were never beaten". This was due in part to having 6 Welsh internationals playing for the team, including Price White, Jeffrey Jones (footballer), Sam Gillam (1890–93), Robert Lee Roberts (1891-1902) and the charismatic Leigh Richmond Roose (1900–01), who was capped three times while playing for 'Welsh'. Whilst a number of its rivals developed into professional clubs London Welsh retained its amateur status and when the Amateur Football Alliance reconstituted the Southern Olympian League in 1921, following the First World War, 'Welsh' were one of 15 clubs admitted to membership.
The Southern Olympian League gradually extended its Membership and Reserve XIs were admitted for the first time in 1923-24 and a Minor Section in 1927-28. The status and reputation of the League was greatly enhanced in the seasons between the wars, but in 1939 the Second World War broke out and the League was again disbanded. Immediately hostilities ceased the League was restarted with 8 clubs. The number rapidly increased in succeeding seasons and in 1948-49 it was possible to form three Senior Divisions, Senior and Junior Challenge Cup competitions were introduced in 1948-49, Minor Cup in 1950-51 and a competition for 4th, 5th and 6th XIs in 1953-54.