Why the rusting wreck of a second world war ship is so important to China

The Sierra Madre, deliberately marooned by the Philippines in 1999, is crumbling but repair is being made impossible by an effective blockade by Beijing

It is perhaps the most unlikely kind of military base. For more than two decades, a second world war-era ship, BRP Sierra Madre, has stood deliberately grounded in the remote, shallow waters of the fiercely contested South China Sea, carrying the Philippine flag and guarding against Chinese expansion.

But its future is increasingly precarious, and the ship has become a growing flashpoint in one of the world's most disputed waters.