He was an ardent royalist, is supposed to have defended ship money and billeting of troops, and joined king Charles I of England at Oxford on his retreat thither, but he was one of those judges for whose continuance in office the British House of Commons petitioned in 1643.
After the death of Charles I, Foster lived in retirement, and, being a deep black letter lawyer, practised in the Temple as a chamber counsel and conveyancer.
He had received on 14 October 1656 a license from Oliver Cromwell and council to come to London on private business and stay there, notwithstanding the late proclamation.
Many Fifth-monarchy men and the Quakers, John Crook,[1] Grey, Bolton, and Tonge, accused of a plot against the king's life, were tried by him, and in the case of Sir Harry Vane he not only browbeat the prisoner on the trial, but induced the king to sanction the execution against his inclination and word and the petition of both houses of parliament.
He died on circuit, 4 October 1663, and was buried under a tomb bearing a bust of him in robes, at Egham, Surrey.