Black belly band on Coal Tit?

Hi all I've had daily morning visits from a lovely little Coal Tit in my garden, see pictured. Something is bugging me though, this little birdie has a very distinctive black horizontal band running round its circumference like a belt and it isnt black base plumage its far too dark and uniform. I wasnt aware either males or females have this feature, and hes certainly a Coal Tit because of the white band on his wing and the chin strap too. I cant find anything on bird forums or databases, or the Merlin ID app. Is he just a rare chap. Any opinions welcome!