Appearance:
Medium to large aquatic bird
Largest member of the grebe family
Long neck and head
Long bill
White face with a black line from the base of the bill to the eye
Red eye
Dark olive-green feet

Chestnut feathers on side of head
Black crown and head crest
Dark brown wings
White underparts
White patches on wings
Non-breeding plumage:
No crest or tippets
Dark crown bordered by a white face
White extends down the foreneck and chest
Juvenile:
Striped black and white head and neck
I took these photos in September 2014 on one of our visits to London. I believe they were taken in Regent's Park, as that is my regular stomping ground.
Learn more about the Great Crest Grebe.