The power of subpoena -- broad as it is -- and the power of contempt for refusing to answer -- drastic as that is -- and even the solemnity of the oath cannot ensure truthful answers.
Or it could be a motion to punish the offender - Parliament has a theoretical power to jail people for contempt, and the building does contain a cell for this purpose.
Equally telling was the open contempt directed at him by Conservative backbenchers, who clearly feel the balance of power in the Coalition has swung decisively against the Lib Dems.