It started three months ago with an angry exchange over a bicycle in front of the British prime minister's official residence. Now, the controversy over what a senior politician did or didn't say to officers guarding Downing Street has grown into a full-blown crisis, raising new questions about police ethics.

Writing in The Sunday Times, Andrew Mitchell said he was the victim of a conspiracy, saying that a report which quoted him as describing police as "plebs" — an insulting term for a working-class person — had been faked.

Mitchell resigned as the Conservatives' chief whip in October as the scandal rumbled on, but the arrest of two police officers allegedly involved in lying about the incident has revived his political fortunes — and raised new questions for Scotland Yard.