The role of a revising chamber is to scrutinise legislation that may have been drafted over-hastily in the lower house and to suggest amendments that the lower house may nevertheless reject if it wishes to. An example is the British House of Lords. Under the Parliament Acts 1911 and 1949, the House of Lords can no longer prevent the passage of most bills, but it must be given an opportunity to debate them and propose amendments, and can thereby delay the passage of a bill with which it disagrees. Bills can only be delayed for up to one year before the Commons can use the Parliament Act, although economic bills can only be delayed for one month. It is sometimes seen as having a special role of safeguarding the uncodified Constitution of the United Kingdom and important civil liberties against ill-considered change. The British House of Lords has a number of ways to block legislation and to reject it; however, the House of Commons can eventually use the Parliament Act to force something through. The Commons will often accept amendments passed by the Lords; however, the two houses have sometimes reached a constitutional standoff. For example, when the Labour Government of 1999 tried to expel all hereditary peers from the Lords, the Lords threatened to wreck the Government's entire legislative agenda and to block every bill which was sent to the chamber. This standoff led to negotiations between Viscount Cranborne, the then Shadow Leader of the House, and the Labour Government, resulting in the Weatherill Amendment to the House of Lords Act 1999, which preserved 92 hereditary peers in the house. Compromise and negotiation between the two houses make the Parliament Act a very rarely used backup plan.