The ruins of a 12th Century abbey in South London are on a shortlist of sites in Britain that could get World Heritage Site status.

Merton Priory was one of the most important religious sites in the country, until it was destroyed in 1538.

Now, it is hidden away behind a black door in a subway, underneath a road and next to a supermarket car park.

Rajini Vaidyanathan finds out what it takes to make it into on the World Heritage list, alongside the Tower of London and the Taj Mahal.