Mr. Mercer is giving evidence to an inquiry that is delving into killings allegedly carried out by UK special forces in Afghanistan between 2010 and 2013.
An inquiry at the Royal Courts of Justice in London has been told SAS soldiers killed a number of innocent young men during tours of duty in Afghanistan.
High “operational tempo” and “unrelentingly demanding” operations are combing to “mitigate against Special Forces recruitment”, warns a Brigadier in leaked letter.