Diamond Dove

For the last three days a very small dove, smaller than a blackbird, has been visiting my garden, picking up seed dropped from my feeders.  From the internet I have identified it as a Diamond Dove, which is apparently a fairly common aviary bird.  It appears to be able to look after itself and is areasonably strong flier, so may have been in the wild, (if London counts as wild!), for a while.  Has anybody else seen examples of this bird?  Could it be the next exotic colonising us, like the ringnecked parakeet?  It seems to be better behaved that them!