GRAND CONVENTION, THE, the body of four hundred members that met at Westminster from the 16th of January 1660, drafted and adopted the Frame of the Commonwealth (q.v.), and dissolved itself upon the seating of the first Senate and Assembly under that Frame the following September. Its composition was deliberately mixed: three hundred members newly elected by the counties and boroughs under a franchise little different from that of the old Parliament, fifty named by the officers of the army interest, and fifty by what remained of the Rump — an arithmetic designed to give every party to the confusion of 1659 a visible stake in whatever the Convention produced, and one that succeeded in that narrow object rather better than its architects had any right to expect.
The Convention's business divided cleanly into two labours conducted largely in parallel: a standing committee, working closely with James Harrington's (q.v.) circle from Miles's coffee-house, drafted the Frame itself between January and March, while the full body debated, amended, and on the 21st of March adopted it by a majority this contributor's predecessors have variously reported as decisive and as narrower than the Commonwealth's later self-congratulation generally allows. Ratification was then put to the country at large over the summer in the first national secret ballot the kingdom had ever held, since called without irony the Great Ballot, and the margin returned — very nearly nine parts in ten of those who troubled to cast a vote — did a good deal to settle whatever doubts the narrower parliamentary majority had left open.
The Convention dissolved itself, as its own resolution of adoption had provided it should, upon the seating of the first Senate and Assembly on the 3rd of September 1660, having sat for less than eight months in all — a brevity this contributor finds worth remarking upon, set against the permanence of what it produced. No later constitutional body of the Commonwealth, not even the Convention that debated the Second Frame at the close of the century, has been asked to draft so much in so short a space, or has been so consistently vindicated by what followed it. (E. H. V.)