Mystery Bird

On Sunday 2006/09/17, I noticed a "mystery" bird feeding in my garden amongst laughing doves and redheaded finches. Being slightly smaller than the redheaded finches, my first thought was that it may be an leucistic pintailed wydah, but the only clear markings does not match either the male or female, nor any other SA seadeater.

Unfortunately the photographs are not of a very good quality, as they were shot through the scope, but they are good enough to see the markings clearly.

It is all white, with a hint of a greyish tint at the head. It has a heavy, bright orange bill and bright orange legs. At the base of the bill there is a clear black line, as well as a black "tearstripe" running vertically down from each eye.

So my question to the experts are: is this an leucistic southern african bird or some or other escapee?