Adams was founded in 1656 by Alderman William Adams, a wealthy City of London merchant and haberdasher, who was born in Newport and whose younger brother Sir Thomas Adams became Lord Mayor of London. Adams had no children and never married, so therefore decided to leave a bequest for the foundation of the school, which was first opened on 25 March 1656, during the politically unstable and volatile period of the English Interregnum. Having received permission from Oliver Cromwell to found the school, Adams sought to further ensure the school's continued existence by appointing the Master and Wardens of the Haberdashers' Company as governors in perpetuity. As one of the few schools founded during the Interregnum period, the school's articles of foundation were reconfirmed by Act of Parliament in 1660, upon the Restoration of the Monarchy; a copy of which is held in the school archives.