He was the third son of Sir William Slingsby of Kippax, West Yorkshire and was educated at Exeter College, Oxford.
Slingsby introduced the idea of stamping the inscription "Decus et Tutamen" around the edge of silver coins to prevent clipping.
[1] The position of Master was normally held for life, but in 1680 Slingsby was suspended from office on the grounds of incompetence.
His financial accounts were so faulty that he was suspected of fraud and his property temporarily seized to make good the losses.
The duties of Master were then executed by a commission pending Slingsby's resignation in 1686.