The Sharp-angled Peacock needs separating from the Peacock. Several of the methods described are unreliable, or difficult in worn specimens. In the Sharp-angled Peacock the sub-terminal band is more distinctive and is clearly visible from below, in the Peacock this band is more subdued and not prominent from below.
Sharp-angled Peacock (Macaria alternata) - Underside
Caught 2/7/2012, The Hidden House, St Margaret's at Cliffe.