The piece, called Hahn/Cock, is 4.72m high and bathed in brilliant electric blue and has been created by German artist Katharina Fritsch. It'll be on display for the next 18 months.
Thinking about it a bit more, a cockerel makes lots of sense. It's flamboyant, strong, brilliant, confident, forward-looking, full of personality. It's also a bit cheeky. After all, it's a big blue cock. So let's not pretend this is some highbrow, holier-than-thou project. It's poking a bit of fun, too.
The cockerel is an (unofficial) national symbol of France and the title of the piece ('hahn' is German for 'cock') is a deliberate double-entendre.
Speaking to the Guardian, Fritsch said: “It's a nice humorous side-effect to have something French in a place that celebrates victory over Napoleon."
“I think the English have a great sense of humour. I know they like to play games with language. They like their double meanings. So I wanted to play around.”
The once-vacant plinth has become a showcase for temporary artworks over the past few years and Fritsch's sculpture was chosen from a shortlist of six potential occupants. The idea behind the Fourth Plinth Programme is that art is for everyone, it aims to trigger debate about art in public spaces.
Fritsch's sculpture follows works by the likes of Marc Quinn and Yinka Shonibare in finding a temporary home on the plinth, while Antony Gormley encouraged members of the public to take a turn as part of his 2009 commission.
What do you think of Hahn/Cock?
Hahn/Cock by German sculptor Katharina Fritsch is on display at Trafalgar Square's Fourth Plinth until January 2015.