Blue cockerel takes roost on Fourth Plinth

The sculpture has been described as a "domestic cockerel with a twist"

Hundreds gathered in Trafalgar Square to see the artwork unveiled

It was designed by German artist Katharina Fritsch

Mayor Boris Johnson entertains the artist with his pithy bon mots

The new artwork for the Fourth Plinth in London's Trafalgar Square, a bright blue cockerel symbolising regeneration and strength, has been unveiled.

Titled Hahn/Cock, the 4.72m high piece is by German artist Katharina Fritsch and will be on display for 18 months.

Saturated in intense ultramarine blue, the sculpture was unveiled by Boris Johnson, Mayor of London, on Thursday.

It replaces a 4.1m high bronze of a boy on a rocking horse that had been on the plinth since February 2012.

The public sculpture, said Mr Johnson, "doesn't just show that we're the sporting capital, but we are also the artistic and cultural capital of the world".

He also said he would try and avoid any double entendres when talking about the cockerel.

"It is a ginormous blue Hahn Cock, as it's called," he told BBC London.

"I think if you tried to Google it in the future, the Prime Minister would stop you from finding it" - a reference to David Cameron's proposals to have internet pornography blocked by internet providers.

One London-based conservation group had tried to stop the cockerel - a traditional emblem of France - from being displayed.

Trafalgar Square takes its name from the 1805 Battle of Trafalgar, one of Britain's most significant naval victories in the Napoleonic Wars.

The Thorney Island Society wrote to Westminster Council in protest, branding the sculpture "totally inappropriate".

But Justine Simons, director of the Fourth Plinth programme, said she was confident it would be a popular addition.

"We really love the striking vivid blue colour and also the character is really interesting," she told BBC London.

"It's an everyday kind of object - this regular domestic cockerel with a twist. The artist has supersized it.

"It will be as big as a London bus and she's made it this striking blue colour, so it will be familiar but also quite surreal."

Many leading artists have bid to have their work displayed on the Fourth Plinth over the last seven years.

The first sculpture to occupy it was Mark Wallinger's Ecce Homo, a marble sculpture of a human-scale Jesus.

Others have included a statue of a naked, pregnant woman with no arms and Antony Gormley's One & Other, where members of the public occupied the plinth for an hour at a time.