Boris Johnson admitted today he had known nothing of the history of the vacant fourth plinth when he backed a memorial to war hero Sir Keith Park in Trafalgar Square.

The Mayor said he was now throwing his weight behind the scheme to have contemporary works of art on the plinth.

He was speaking as he viewed the current shortlist of six artists for the installation, including Antony Gormley, Anish Kapoor, Tracey Emin and Jeremy Deller, with Ekow Eshun, the artistic director of the Institute of Contemporary Arts and new chairman of the Fourth Plinth Commissioning Group.

Mr Johnson said: "I think the fourth plinth project, the way we have rotating wonders of modern art, has entered the hearts of London. People love it. I want to keep it."

Instead of a permanent memorial to Sir Keith, a New Zealander who helped defend London against aerial bombardment during the Battle of Britain, he was now proposing a temporary statue on the plinth on the 70th anniversary of the battle in 2010.

A permanent memorial to Sir Keith should be erected in an alternative "prestigious" London location, he said.

The next two commissions for the plinth are due to be announced on 23 June.

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