The statues will undergo tests before being repainted

The nine-foot high figures have stood on top of Cardiff Castle's ornate clock tower since 1873.

Carved in stone and painted in vivid colours the statues represent planets and zodiac signs.

Work on the statues has been undertaken as part of an �8m programme of conservation at the castle.

The seven statues, which represent Mercury, Luna (moon), Mars, Jupiter, Saturn, Venus and Sol (sun), were carved by Thomas Nicholls in the late 1800s as part of architect William Burges' designs for the castle.

The 3rd Marquess of Bute had commissioned Burges to carry out renovations at the castle and incorporated his interest in astrology and medieval art.

Carving the statues began in 1869 and they were painted for the first time in 1873.

Over the years there statues have been repainted several times after being exposed to the elements.

The figures represent different planets and zodiac signs

But this is the first time that expert analysis and research has been carried out on the figures, which are considered to be a rare example of painted exterior sculptures.

Karen Morrissey from Hirst Conservation has been working on the statues.

"It is very exciting to investigate the clock tower statues which embody the design ethic of the interiors of the castle and enjoy a prominent position in the Cardiff skyline," she said.

"We are very lucky to have access to Burges' original designs, through the castle archives, which guide more detailed research.

"We have now taken numerous small samples from the figures, which will be assessed under the microscope in order to identify the original colours and decorative techniques."

She said that she hoped that the statues could be restored to their "original glory".

Work on the statues will include repainting and redecoration with gold leaf after research on the decorative layers that have been applied over the years.

It is hoped that the original design will be revealed during the analysis.

John Edwards, who is managing the conservation project said: "The process has only just begun but already we can see that the colour and pattern of the clothing has changed since 1873 - and not as a result of fashion!

"Burges' decorative work was highly intricate and as with surfaces elsewhere in the castle, changes have occurred over time."

The work on the statues is part of an �8m conservation project at the castle and a grant of �5.7 from the Heritage Lottery Fund was awarded for the work.

The total project is expected to be completed in 2008.