New Tate Modern art gallery pyramid extension unveiled

Tate Modern's new extension, a pyramid-like tower that transforms London's skyline, has been been unveiled ahead of its official opening.

The galley is a long way from the Welsh Valleys, but art from the area will soon be showcased there.

David Sillito reports.

New Tate Modern: Switched On is on BBC Two on 18 June at 21:00 BST.