I don't 'know' it wasn't wild but I do know that the average dispersal natal dispersal distance for RNPs is just
1km.
From personal experience I am struggling to agree with this statement.
I have written the RNP segment in the Herts Bird Report since 1998. I also live in SW Herts in the heart of the area where RNP's have colonised in just the last few years. The first mention of them potentially breeding in the county was around 2006 when there were just 42 records in the county. Just look at
http://www.hertsatlas.org.uk/2008/RI.shtml. My first sighting in SW Herts was in 2005, and I have actively birded the area for well over a quarter of a centuary. Now there is hardly a day goes by when I don't record this species in the county in SW Herts. The 1992 report had just 4 sites with the occasional bird on the odd date and it was first recorded in 1985 in the county.
Compare the above with the winter atlas
http://www.hertsatlas.org.uk/2007/RI.shtml when they explore new potential areas.
As this is a Norfolk thread -they are heading your way but it is likely to be many years before you get them in any numbers so enjoy your lack of RNP
While you can (tongue in cheek). They will eat you out of house and home, spoil some of your birding encounters by their aggressive behaviour even with Cuckoo's but can be fun to watch as well.