Fixed-term Parliaments Bill

The noble Lord has been a doughty defender of the constitution for many years in both Houses. I respect him very much for that and I have expressed that view previously. Can he explain to your Lordships why he now thinks, after 100 years of experience of a quinquennial maximum for Parliament, we should suddenly make a radical change to a maximum of four years? What particular experience over those 100 years has changed his attitude?