Letters From Home

<spoiler> The clue above the entry box means to look at the name of the hotel: datoname hotel = day to name.

So take the day of the month given in the post marks, and then take the country name on the stamps. Sometimes you'll have to figure out the country.

Apply the number to the name like this: Nov 7 + United States = United States = S

You get "St Paul's Cathedral".

The hint from the london projection is "Photographer"

Answer: HERBERT MASON . He took the photograph of the 1940 bombing of St Paul's Cathedral in London. </spoiler>