Sinjuns Grammarians Football Club can boast a rich heritage which includes victory over an FA Cup winning club, former players who have represented their respective countries, and numerous amateur football titles.

The club derives from two former - Sir Walter St John School and Battersea Grammar School . Both schools had clubs teams for former pupils (Old Sinjuns FC and Old Grammarians FC), which in 2005 merged to become Sinjuns Grammarians FC.

As the present club does now, both Old Sinjuns and Old Grammarians clubs played at Trinity Fields, formerly known as the Sir Walter St John playing fields. Trinity Fields was originally purchased from London Welsh Rugby in 1918, where it was used as playing fields for Sir Walter St John and Battersea Grammar Schools until those schools closed. In 1995 the Trinity Fields Trust was created to ensure continued use of the grounds as playing fields for the clubs and future generations of club members.