THE OTHER DAY we came across the most charming bookshop — there were books on Paris from the 1800’s, with clothbound and gold foil debossed covers shimmering in the light; there was a tiny art gallery in the back corner and wallpapered ceilings throughout . . . And simply could not leave without a few old books — one on the history of impressionism, and the other, found by P, on the stately homes of Britain.  It was in this one that we discovered the photographer, Henry Dermot Ponsonby Moore, 12th Earl of Drogheda, known professionally as Derry Moore . . .