Despite what the public thinks of its politicians, it is very rare for an MP to be convicted of an offence serious enough to draw a prison sentence. The last sitting MP to go to jail was John Stonehouse, below, more than 30 years ago.
He was a Labour minister whose business affairs went belly up in 1974. He feigned suicide by leaving his clothes on a Miami beach. A month later, Australian police arrested an Englishman whom they thought might be the runaway peer Lord Lucan. It was in fact Stonehouse. He was still an MP while in prison awaiting trial for fraud but once he had been convicted, and sentenced to seven years, he had to resign, or he would have been expelled.
The last MP to be formally cast out, as opposed to resigning in disgrace, was a Tory, Peter Baker, who was elected in 1950, aged only 28. He started forging documents to avoid bankruptcy when his companies ran into trouble, and was expelled in December 1954.
In 1947, Garry Allighan, a journalist turned Labour MP, wrote a sensational article alleging that MPs were selling parliamentary secrets to newspapers. A committee of investigation found two culprits, one of whom was Allighan. MPs voted 187-75 to expel him.
One of the great political comebacks of the century was by the Liberal MP, Horatio Bottomley, who resigned in 1912 because he had gone bankrupt after narrowly escaping jail for fraud. He re-emerged as an ultra-patriotic journalist during the war, used money from the sale of war bonds to discharge his bankruptcy, and was elected as an independent in 1918. At his next trial for fraud, in 1921, he was sentenced to seven years. He was the first MP expelled from the Commons that century.
The former cabinet minister Jonathan Aitken might have become the fourth when he drew an 18-month jail sentence in 1999 for perjury but he was spared that particular disgrace because he had unexpectedly lost his seat in the Labour landslide two years earlier.
Jimmy Thomas, one of the few Labour ministers to serve in Ramsay MacDonald's coalition government, resigned after being caught in 1936 leaking budget secrets to his son, a stockbroker. A Tory, John Cordle, resigned in 1977 over his links with the corrupt architect John Poulson.
Two other 20th-century MPs had to resign after being convicted of what were thought then to be serious offences. Arthur Lynch, an Irish MP, was sentenced to be hanged in 1903 for fighting against the British in the Boer War. The sentence was commuted and he was back in the Commons after six years. Sir Paul Latham, a Tory, went to fight the Nazis, was caught having gay sex with fellow soldiers, and was sentenced to two years. By our standards, neither man had done anything wrong.