Hemel (BMT): Finally managed to confirm a 4th Kingfisher along the river Bulbourne through BMT land. I've had a suspicion that a second (immature) female was around but just hadn't been able to see both birds at the same time. Neither bird had distinguishing features to ID them individually, unfortunately. Anyway, chuffed to sort that out today. Didn't manage a photograph of the second female but it didn't matter.
So, we have 2 ♂ and 2 ♀. One male has the malformed upper mandible and is fairly tolerant of people; the other male is more secretive and keeps to the more sheltered areas away from pedestrian traffic. Similarly, one female is very tolerant of photographers and admirers. She is drawing in the crowds and developing a bumper portfolio on Flickr. The second female is more timid and I've not been able to photograph her.
From left to right: timid ♂, confiding ♂ (protruding upper bill) & confiding ♀