JK0060PH,Sg 43,1d Red, plate 125. Envelope addressed to the Duchess of Inverness (Cecilia Underwood) to Kensington Palace. Dated May 26th 1872. Sent from Aberdeen. Scarce Royal postal History. She was a mistress of Prince Augustus Frederick, Duke of Sussex.(Sixth son of King George III) Despite marrying,their union was in contravention of the Royal marriages act of 1772 and as such was considered legally void.