Tory MP Crispin Blunt's decision to resign as a junior opposition frontbench spokesman will have come as a surprise to many in the party.
The timing of his departure - distracting attention away from the party's good performance in the local elections - will have only rubbed salt in wounds, as will his scathing attack on the Tory leader's abilities.
Like Iain Duncan Smith, Mr Blunt was educated at the Royal Military Academy, Sandhurst, and went on to have a successful military career before entering politics.
Tory MP Crispin Blunt
He has risen through the ranks of the Conservative Party relatively quickly since entering Parliament in 1997.
The 42-year-old MP for Reigate was appointed a member of the Commons Select Defence Committee, where he could draw on his military background.
He also served on several other important parliamentary committees, and was
elected secretary of the Conservative Foreign and Commonwealth Affairs Committee
and the Conservative Middle East Council.
After increasing his majority at the last general election, Iain Duncan Smith, the then newly elected leader, appointed him to the front-bench as a Northern Ireland spokesman.
He did well enough to earn promotion in July last year, being appointed to the number two position in Tim Yeo's shadow Trade and Industry team.
Despite his hawkish tendencies on defence matters, he is something of a Tory moderate, having supported Michael Ancram's bid for the leadership, and is liberal-leaning on some social issues, such as abortion and stem cell research.
He can, however, be boisterously partisan in the Commons chamber and was one of a handful of MPs to vote against Michael Martin's election as speaker.
A former captain in the Royal Hussars, Mr Blunt was educated at Wellington College, Berkshire, and the Royal Military Academy,
Sandhurst, where he won the Queen's Medal.
He went on to read politics at the University of Durham between 1981 and 1984, being elected president of the Union Society in 1983.
He was commissioned into the 13th/18th Royal Hussars (Queen Mary's Own) in 1979 and served until 1990, his postings including Cyprus and Germany.
Among the positions he held were troop leader, regimental operations officer, and armoured reconnaissance squadron commander.
He resigned with the rank of captain in 1990 and obtained an MBA from Cranfield Institute of Technology the following year.
In 1992 he made his first, and unsuccessful, bid to win a parliamentary seat, contesting West Bromwich East.
In 1993, he was appointed as special adviser to the then Defence Secretary, Malcolm (now Sir Malcolm) Rifkind.
He followed Mr Rifkind as special adviser when he became Foreign Secretary in 1995.
Married with two children, Mr Blunt is a keen cricketer, having played for the Lords and Commons team and the Reigate Priory Cavaliers.
His other interests include travel, bridge, food and wine, and historical novels.