" Oh, I've been underground, " said Lupin. " Almost literally. That's why I haven't been able to write, Harry; sending letters to you would have been something of a giveaway."
" Ah, you are sending off a letter, Princess? I have already dispatched mine. I have written to my poor mother, " said the smiling Mademoiselle Bourienne rapidly, in her pleasant mellow tones and with guttural r's.
We're stopping in Port Lockroy which has the world's southern most post office and apparently there's a little gift shop there where you can buy postcards and postage and mail letters.