S7 21381/82 has finally been delivered to London having lain at Derby as a 6-car train since autumn 2013, as its M2D car was donated (in autumn 2012) to 21319/20 to make this an 8-car train for temporary use on the Metropolitan Line.
Is 21319/20 back to being an S7 or did Bombardier build an extra carriage? I think that one S7+1 will be permanent and the rest reformed to original config?