The Salisbury Convention reference article from the English Wikipedia on 24-Apr-2004
(provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Salisbury Convention

Helping orphans the way you would do it
The Salisbury Convention is a constitutional convention in the United Kingdom that means that the House of Lords will not oppose any government legislation promised by its election manifesto.

It was introduced by the Conservative leader of the House of Lords, Lord Salisbury in 1945 following a landslide Labour general election victory. Salisbury believed that because Clement Attlee's Labour government had a clear mandate to deliver the policies of nationalisation and welfare state measures, the House of Lords should not oppose such legislation at the second reading.