There he worked as an assistant at the Bodleian Library until 1700, when he moved to London, where he gained temporary jobs as secretary to the SPCK and assistant to Hans Sloane (Sloane was secretary to the Royal Society, and Wanley was elected a Fellow of it in 1706), before landing a settled job with the Harleys which he held to the end of his life.
Anstis was an indefatigable antiquarian whose correspondence with fellow scholars such as Thomas Hearne and Humfrey Wanley testifies to his wide interests.