Strange exotic bird turns out to be a wren carrying dead bracken fronds.

 An exotic looking bird this morning turned out to be a wren struggling with dead bracken.  It has moved into an armour-plated nest box, formerly occupied by Great tits.
Why armoured?  Please see https://sussexrambler.blogspot.com/2016/05/woodpecker-proof-nest-box.html for the gruesome reason.

It is making frequent flights bringing nesting materials.