House of Commons
Robin Cook resigned as leader of the House of Commons over the government's policy on Iraq in March 2003.
His announcement came the day before a government motion in the Commons seeking support to go to war in Iraq. Two days later the UK would join the US-led invasion.
Mr Cook was the first minister to resign over Iraq but within a day of his announcement junior health minister, Lord Hunt of Kings Heath and Home Office minister John Denham swiftly followed suit.
By May, the issue of Iraq had claimed a fourth resignation, when Clare Short left the job of international development secretary.
It was the first time that Mr Cook had addressed the House of Commons from the backbenches in 20 years and his resignation was seen as particularly significant given the five years he spent working for Mr Blair as foreign secretary.
During the speech Mr Cook took the opportunity to defend and support the prime minister and denounced those MPs wishing to use the crisis to displace Tony Blair. He expressed his sadness at resigning a decision, he said, he had reached "with a heavy heart".
Widely known as a great Commons orator, Mr Cook's speech was met with rapturous applause and the former leader of the House received a standing ovation from several MPs.