White Ibis Eudocimus albus
There have been a number of records of escaped White Ibises in Europe but when a juvenile turned up in Kent in 2014 some people started to take seriously the possibility of it being a genuine vagrant from North America. Positively there have been a number of extralimital records within North America, however it is not a long-distance migrant and does not seem a particularly likely candidate for vagrancy to Europe. On the other hand it seems that the species is - or at least has been - bred in captivity in Europe, at least in Germany and perhaps also in the Netherlands and elsewhere, so perhaps that is a more likely origin.
The first few photos below were taken in Florida where the species is extremely common, and the remainder are the Kentish bird.