Rainsford was one of Sir Matthew Hale's colleagues in the commission which sat at Clifford's Inn between 1667 and 1672, under the Fire of London Disputes Act 1666 to determine the legal questions arising out of the rebuilding of the quarters of London destroyed by the great fire. In the meantime he was transferred to the king's bench, 6 February 1669, and on 12 April 1676 he succeeded Hale as Chief Justice of the King's Bench. On the return to Lord Shaftesbury's writ of habeas corpus he decided, 29 June 1677, an important point of constitutional law, viz. that the courts of law have no jurisdiction, during the parliamentary session, to discharge a peer committed by order of the House of Lords, even though the warrant of commitment be such as would be void if issued by an ordinary tribunal. Raynsford was removed to make room for Sir William Scroggs in June 1678.