High up on the ceiling of Christ Church Cathedral in Oxford are hundreds of miniature carvings but perhaps surprising for such a splendid building, many of them are not just old; by the cathedral's own admission, some are plain 'ugly'. 

They're too high up in the vaults for anyone to get a good look at them but, as a treasured part of the building's architectural heritage, all 576 of the 'bosses' are being inspected by the cathedral for the first time in half a century. 

The bosses are the size of a kitchen tile and mostly made out of oak.  They depict a variety of creatures, from dogs to devils and 'green men' sticking their tongues out. 

It's a painstaking task for the cathedral staff to inspect each one, with the bosses spanning the four bays of the nave but it's essential that they are checked for woodworm and age-related damage to preserve them for generations to come. 

Although the bosses have been a fixture of the cathedral for hundreds of years, they continue to surprise and delight. 

For one thing, several of the bosses have gone missing, having probably fallen off in the past five hundred years. The cathedral is still deciding how to remedy this. 

For Joseph Denby, the cathedral's operations manager, it's the sheer variety of designs that the medieval carvers went to the trouble of making, all the while knowing that they would be too out of view to be enjoyed by worshippers in the pews below.

Despite the centuries that have gone by, he says the quality of the carvings can still be seen. 

'Every single boss is being checked by our team of specialist restorers,' said Mr Denby. 'I think they've been quite surprised by the sheer variety of designs they've come across.' 

Some of the bosses appear to have been made by re-using wood that originally came from an earlier version of the building, but not all of the bosses are medieval. Some are more recent, having been made from soft wood in the nineteenth century.

Where the old nails that fixed them into place are too rusty, they are being taken down and replaced with new stainless steel screws to keep them secure long into the future.

The work is part of a major restoration project to survey the roof and plaster work of the cathedral, as well as clean and repair the fabric of the building, which dates back to the 12th century. 

Part of the restoration includes the installation of a new energy efficient lighting system to help reduce the cathedral's carbon footprint.

'The quality of the carvings is fantastic,' Mr Denby continued. 

'It's hard to choose a favourite because they are all extraordinary. But I admit to having a soft spot for the Dog in the Bush [above] as it reminds me of my own dog Sky.'