Trust between UK and Afghan troops
Eighteen foreign soldiers have been killed by members of the Afghan military since the start of the year. The latest to to be killed was last Friday.
The Taliban says it was behind some of the killings, but others are down to cultural differences and antagonism between foreign troops and their Afghan allies.
The BBC's Kabul correspondent, Quentin Sommerville, has been out with the British troops working alongside the Afghan Army, to see how the deaths are affecting relationships between the troops.