This is a postcard with a photograph of Fowey Harbour, in Cornwall, with an arrow drawn upon it, presumably by Manning to let Darby know whereabouts he was staying for his holiday.
Manning says he expects to be back in College by next week, although he'll be in and out for the rest of the Summer. He reminds Darby that he hasn't forgetting the 'vast sums' that he still owes him. Finally, he briefly mentions that he has a good fishing story to tell Darby so fishing may be one of his hobbies.
Manning, Bernard L.