British first class is not Europe first class

I presented what Royal Mail put on unsufficient franked postcard. But, what can it do when the card is not illustrated ?

The éditions Verdier is a French publisher. Inside their books, the reader find a card with a quizz : who are you ? what did you buy ? where ? etc.

The problem of postage due is indicated by a big cancellation beginning with the word "DELAYED" : certainly a message explaining why Royal Mail did not hurry to treat this card for three days.