Poly had been found by a neighbour on the other side of Fairy Hill Park, who lives on Broad Lawn, a lady also called Jenny. Jenny Broad-Lawn had fed the strange, tame bird, and taken her in. As she was going into hospital that afternoon she phoned the RSPCA, who took young Poly away. When the RSPCA found out she was ours the lady brought her back after inspecting our duck pen, which she pronounced truly an Edenic environment for two Muscovies.
So Poly was returned. Apparently there were posters advertising her 'found' status on the other side of the park - we hadn't seen them as we were in Denmark, plus we only sometimes walk to that side of Fairy Hill, we usually go the other way up to Eltham.
Hurray! Here's a picture of Poly and Sharik enjoying morning ablutions, a bowl of hot water on a frosty morn.