A British soldier was killed in Afghanistan after being hit by fire from a US Apache helicopter which wrongly identified his base as an enemy stronghold, a coroner said.
Lance Corporal Christopher Roney, 23, of 3rd Battalion The Rifles, died from head injuries he suffered while serving at Patrol Base Almas, in Sangin, Helmand, in December 2009.
The base had come under attack from insurgents and the platoon based there were busy fighting them off when air support was called in, Coroner Derek Winter said.
A drone fitted with a camera and two US Apaches flew to the patrol base, which was a compound with mud walls, bought from a local owner some weeks before and was not on official maps.
British troops on the ground, who by this stage had won a firefight against their attackers, were incorrectly identified as the enemy and they were hit by 30mm chain gun rounds.
Mr Winter, the Sunderland Coroner, said 200 rounds were fired before the mistake was spotted, leaving 11 injured on the ground.
L/Cpl Roney, a married former drayman, received emergency treatment but died from his injuries the next day.
Mr Winter said the mistaken view that the British base was an insurgents' compound was shared with key personnel. This was despite the patrol base, 3km from Forward Operating Base Jackson, having a flagpole, a washing line, defensive constructions and personnel who were not dressed like the enemy, Mr Winter said.
He was summarising the evidence he expected to hear during the week-long inquest. Statements have been given from the US pilots and co-pilots which will be read later.
Retired Lieutenant Colonel Nicholas Kitson, who watched live pictures of the attack, said it was a "tragic incident".