The Lords doesn’t actually have the power to veto bills thanks to the Parliament act. They also have a principle of ultimate legislative priority under which they defer to the commons in matters where the commons puts its foot down. They generally act as a revising body rather than outright attempting to defy the commons.

   > Under the Parliament Acts 1911 and 1949 it is possible for a bill to be    presented for Royal Assent without the agreement of the House of Lords, provided that certain conditions are met. This change was seen by some as a departure from Dicey’s notion of sovereignty conferred upon a tripartite body.

On the other hand, the process of having Commons legislation rejected by the Lords, then amended and sent back can take almost a year. A government looking to push its legislative programme in a single parliament may choose to remove the most controversial elements in return for an easier passage through the Lords. In this way, just the threat of Lords scrutiny can be enough to moderate the output of the Commons.