By Jessica Frank-Keyes Johnny Mercer has been given a fresh deadline to explain why he should not have to hand over the names of those who informed him of alleged special forces murders in Afghanistan. The veterans minister submitted an appeal to the Afghanistan Inquiry after he was ordered to provide a witness statement containing the names – or face a potential prison sentence. Chairman Sir Charles Haddon-Cave originally gave the Plymouth Moor View MP until 4pm on April 5 to comply with the order, but this has now been extended after Mercer’s appeal. The minister now has until 4pm on May 8 t…