Small bird black crown white belly with purple -blue breast and white wingbars smaller than blackbird?

Question

larger than robin smaller than blackbird spotted in belfast harbour

Answer 1

more detail needed, I am at a loss. What family of birds did it look like, was it in flight? if so what was the flight like? beak size colour etc? what was the overall colour of the bird, wings, rump etc.???

could it be this?

http://www.wildaboutbritain.co.uk/files/...