"A Survey of the Hippopotamus in Captivity in the British Isles" (John Frost; 1996) gives the date of Gracie's death as 5th December 1944; this is also the date given by Gerald Iles in his book "At Home in the Zoo" (1960).
However, according to the European Hippo Studbook the date was the 3rd December 1944.
It's interesting to see that the museum confirms the date of 5th December 1944.
