1956 1d Violet Blue Postage Due St. Edwards Crown Watermark used on First Day

7th June 1956, 1d Violet Blue Postage Due, St. Edwards Crown Watermark used commercially on First Day of Issue. The cover was posted in Glasgow on the 5th June, with 1½d Wilding and received the 1d postage due cancelled with a London cds. The postage rate increased on 1st June 1956 to 2d. Hence double the difference (2 x ½d) 1d Postage Due was applied by regulations + 1d To Pay Cachet. Good condition. Clear date on the cds. VERY RARE FDC. Catalogued £950 in Collecting British First Day Covers 2022 by Adrian Bradbury.