Because he thought Cyril Smith was next.
They don't make Liberal MPs like that any more - working class, ran a company - not only that, but a company that made things, anti-abortion, pro-capital punishment. Even in the 70s he was a rarity in a party becoming dominated by career politicians.
"Spurred on by the chip on his very large shoulder, he saw it as his duty to fight for the rights of the common man. He was deeply proud of his modest Lancashire origins, and never let anyone forget it.
A shade puritanical, he had far more affinity with the lower middle class than with a Liberal establishment — the Bonham Carters, Thorpes and Grimonds — which he despised. He was the only Liberal to oppose the abolition of capital punishment and abortion law reform (“We are the backstreet abortionists for the rest of Europe,” he declared)."