Pigeons at dawn.... (first published 1936)
Much ingenuity is exercised in devising a communication system with homing pigeons - Mrs Blackett is remarkably tolerant about the final arrangement which involves a loudly clanging bell whenever a pigeon deigns to return to its home (the dilatory and unreliable Sappho comes home at 5am). And the long-awaited arrival of the armadillo, Timothy, is delightful.
I wasn't a huge fan of Ransome's books when I was a child, but I am making up for it now, partly, I suppose, because it makes me rather nostalgic for the days when children had freedom to go off with a tent and quantities of revolting things in tins, without the feeling that adults were peering over their shoulders all day. I felt especially wistful at the idea that a group of children would amuse themselves far into the night by singing campfire songs. The sun used to shine in those days, too.