Dan Cruickshank: 'Palmyra's fall to IS appalling'

There is growing concern about the fate of one of world's most important archaeological sites.

Fighters from Islamic State have entered the ancient city of Palmyra in Syria, according to reports.

The militants have already destroyed sites in Iraq that were built before Islam - and the fear is they will do the same to Palmyra.

So far, it is is believed the site, on the road between the capital Damascus and the eastern city of Deir al-Zour, is still intact.

One of the UK's top experts, the historian Dan Cruickshank, explains Palmyra's significance.