 By 1865 he was a Major.Although the smaller Lancashire AVCs were grouped together into administrative battalions, the 15th remained independent, although between 1863 and 1867 it was attached to the Manchester-based 19th Lancashire AVC for administrative purposes.As the unit expanded, Mewburn was superseded in command by the local linen merchant Robert Trimble, who joined from the Liverpool Irish and had financed the raising of the third battery.