A measure proposed by the Long Parliament and reluctantly given the King's assent which ensured a parliamentary sitting of at least 50 days every three years. It was intended to prevent the King attempting to rule without Parliament as he had during the 1630s and as protection against the King arbitrarily dissolving Parliament. King Charles regarded it as contrary to the royal prerogative.
The Act was passed in February 1641. Within a year the first Civil War had erupted and it was never used until 1660. It was repealed in 1664.