Image caption Louis Smith's Holly was inspired by the Greek myth of Prometheus Louis Smith's oil painting Holly was inspired by Greek myth In pictures: Portrait Award finalists

An eight-foot high portrait of a naked model handcuffed to a rock has been shortlisted for the National Portrait Gallery's annual art prize.

Louis Smith's artwork is in the final running along with Ian Cumberland, Wim Heldens and Sertan Saltan for the £25,000 BP Portrait Award.

More than 50 portraits have been selected for the annual exhibition at the London gallery.

The prize winner will be announced on 14 June.

In addition to the £25,000 prize money, the winner will receive a commission worth £4,000.

A further £5,000 awarded to a young entrant aged between 18-30, for which both Cumberland and Saltan are eligible.

Mr Smith, who said his artwork Holly was inspired by the Greek myth of Prometheus, called it "a message of composure in the face of adversity".

Turkish-born Saltan's piece was of a young woman with her hair in rollers and carrying a large knife during Thanksgiving preparations.

"The contrast of knife, gloves and rollers brought both humour and horror to mind," he said.

Distracted, by Heldens, is of a portrait of his friend Jeroen, a 25-year-old philosophy student who has sat for him more than 20 times.

Cumberland said the title, Just To Feel Normal, refers to his sitter's response when asked "why he continues along his chosen path".

Gallery director Sandy Nairne said: "The diversity of styles in the shortlisted portraits and the skill of the works selected from this record entry to the BP Portrait Award show how contemporary portraiture remains an energetic and telling force."

Last year the award was won by former teacher Daphne Todd for a painting of her 100-year-old mother's corpse.