An iconic statue of the Duke of Wellington with a traffic cone on his head has turned partly green due to a mysterious algae.

Tourists were left puzzled after parts of the famous statue appeared to turn green overnight.

Now experts have been called in by Glasgow City Council to work out what caused the algae to appear.

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The A-listed Duke of Wellington statue, which stands guard outside the city's Gallery of Modern Art, is famous for the traffic cone that sits on the Duke's head.

But after the mysterious green algae covered part of one flank of the horse and an area of the plinth it sits on, experts were called in to determine the cause.

Until it is known what caused the algae to appear on the statue, it will not be cleaned.

A spokesman for Glasgow City Council said: "We have called in experts to look at the statue to find out what caused the problem."

That won't stop tourists visiting the city taking pictures of the famous statue however, with it being one of the most famous images of Glasgow.

In 2011, the Lonely Planet guide included the statue of Arthur Wellesley, 1st Duke of Wellington, in its list of the top 10 most bizarre monuments in the world.

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The statue has been topped with a traffic cone since the first half of the 1980s and it has become an extremely popular fixture in the city.

In 2013, the council was forced to withdraw plans to double the height of the plinth after widespread public opposition.

A Facebook campaign called Keep the Cone attracted more than 72,000 likes within its first 24 hours.

The statue has proven to be a firm favourite on TripAdvisor where it has a rating of four and a half stars.

One tourist wrote: "You just have to view this and try to understand why a very old statue of a Duke has a traffic cone on its head. This is Glasgow humour at its best."

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Beth Stevens, from Louisiana, USA, said: "I am not sure why he wears a traffic cone but it is a sight to see."

A spokesman for Glasgow City Council said: "The statue will be inspected today (Thurs) and there will follow a course of action dependent on the inspection.

"The damage may have come about because it was a wet summer but it also appears that someone put a cone on the rear of the horse.

"The absence of direct sunlight added to the weather may have affected the overall statue and resulted in the green stuff being there.

"By the looks of it, it may not actually be algae but we will have to await the result of the inspection."