The Old Williamsonian Club exists to promote mutual support between the School, its Trustees and its former pupils and staff. This is achieved by the regular passing of information to all its members by means of at least two postings per year, one of which will include the School Magazine "The Williamsonian".

The Trustees and the School make available to the Club facilities that include the Pavilion. which is used as our Clubhouse, the Sports Hall, the Swimming Pool, the Playing Fields and an All Weather Playing Surface. These facilities, provided at a very generous cost to the Club mean that the Club can offer many sporting and social activities. The Sections of the Club organise the various activities that use these facilities. On joining the O W Club members can join in any or all of the sporting activities.

The club and school share a strong relationship with many events planned throughout the year. One such event is Founders Day which takes place on the first saturday in July.