Blackcap in Hethersett 16th March (An interesting record for discussion)

At 0800 this morning, whilst working in Hethersett, I found a singing male Blackcap in thick Ivy within a mature garden in the village. 
We know that small numbers of Blackcaps spend the winter in Britain, however, studies appear to show that Blackcaps wintering in Britain are birds which have bred in central Europe.  Studies have also shown that not too many 'British' Blackcaps have been ringed/recorded in winter in Britain.
This March has seen early arriving Chiffchaffs on my Breckland patch, the first singing birds being noted from the middle of the second week of March.  Given the good numbers of Chiffchaffs being seen earlier in March, I would like to think that my singing Blackcap this morning in Hethersett is a recently arrived migrant from the south.