June 2015 - originally issued 3 January 2013 with code M12L the M15L version was first found in June. However due to excess stocks at the printers many books with pack dates through to April 2015 were M14L. Some packs were found to have a mix of M14L and M15L, and these M15L books are from packs dated 30/03/15!
12 x 1st class Royal Mail Red booklet , source code MTIL, year code M15L
Printed by Walsall Security Printers with cylinders W7(red) W2 W2
SG GB Concise catalogue - not yet allocated, probably MF7.