In the United Kingdom, the four Boundary Commissions are responsible for determining the boundaries of House of Commons constituencies. There is one Boundary Commission each for England, Scotland, Wales, and Northern Ireland.
The Commissions conduct a review once in eight to twelve years. There are four members of each Commission, of which three actually take part in meetings. The Speaker of the House of Commons is the ex officio Chairman of each Boundary Commission, though he takes no actual part in the proceedings. The Deputy Chairman of a Commission, who actually presides over Commission meetings, is always a Justice in a British court.
Once in eight to twelve years, the Commission conducts a complete review of all constituencies. In between general reviews, the Commission conducts interim reviews, considering one geographic area at a time. The interim reviews usually do not yield drastic changes in boundaries, while the general reviews often do.
Under the rules established by Parliament, the number of constituencies in Great Britain (England, Wales, and Scotland) must not be "substantially greater or less" than six hundred and thirteen. Of those six hundred and thirteen constituencies, at least thirty-five must be in Wales. Meanwhile, Northern Ireland may include sixteen to eighteen constituencies.
The Boundary Commissions are required by law to take local government boundaries into account when determining constituencies. The Commission, however, may choose to deviate from this requirement if failing to do so would cause some constituencies to be widely disparate in size.
Once the Commission makes a report, the recommendations must be submitted to Parliament. The Parliament may approve or reject these recommendations, but it may not amend them. If Parliament approves the recommendations, then the Sovereign makes an Order formalising the boundary changes.