After three members of Britain's Black Watch regiment are killed at a checkpoint near their new base in central Iraq, the BBC's chief political correspondent Mark Mardell outlines the possible political ramifications.
Black Watch soldiers are currently based at Camp Dogwood
Thirty-one British troops have died in action since this war began, but this is the worst incident for 15 months.
It is politically important because it was so hotly contested, so hotly argued against by many MPs at the time.
This is potentially a serious moment for the government for this reason. Remember when the war began and British troops did start to die in action, the politicians here fell silent.
That is the norm, that is the convention. You don't attack the politicians when troops are in action.
But tonight, on the very day these soldiers have died, the SNP has chosen to really go very, very strongly for the government indeed.
It is very difficult in fact impossible at the moment to tell how this will play out, it depends whether other politicians decide to join in, it depends on the public reaction, above all it actually depends on what happens to those troops in Iraq.
It is potentially a serious moment for the government.