A rare Banksy painting with a sharp environmental message is set to go under the hammer at Sotheby’s in London. Crude Oil (Vettriano), a reworking of Jack Vettriano’s The Singing Butler, is expected to fetch up to $6.3 million at auction. (AP Video: Mustakim Hasnath)

A treasured Banksy painting could raise up $6.3 million at auction

A rare Banksy painting with a sharp environmental message is set to go under the hammer at Sotheby’s in London. Crude Oil (Vettriano), a reworking of Jack Vettriano’s The Singing Butler, is expected to fetch up to $6.3 million at auction. (AP Video: Mustakim Hasnath)