The organisers of Britain's most valuable non-fiction literary prize have announced their "longlist" of 21 candidates.

The BBC Four Samuel Johnson Prize rewards the best in non-fiction from biographies and travel to science and arts books, with the winner receiving �30,000.

The entries include Miranda Carter's biogaphy of spy Anthony Blunt, Roy Jenkins' Churchill and Trieste and the Meaning of Nowhere by Jan Morris.

BBC broadcaster David Dimbleby will be chairing the panel of judges.

Also on the panel will be Sunday Times literary editor Caroline Gascoigne, writer and critic Bonnie Greer, geologist and scientific writer Richard Fortey and Enigma author Robert Harris.

War studies

The next step will be to whittle down the list of 21 authors down to a shortlist of six in early June before the winner is announced on Monday 24 June.

The first winner - in 1999 - was Anthony Beevor's Stalingrad, and The Third Reich: A New History by Michael Burleigh picked up the prize last year.

The single volume work is a radical re-examination of the Third Reich, which charts the rise of Nazi Germany, recreating life under a totalitarian dictatorship.

Digital arts and culture channel BBC Four recently announced it would sponsor the award and televise the ceremony in a three-year deal.

It is open to books in the areas of current affairs, history, politics, science, sport, travel, biography, autobiography and the arts.

The full "longlist" is:

Old Man Goya by Julia Blackburn

Anthony Blunt: His Lives by Miranda Carter

Captain Cook by Vanessa Collingridge

The Voices of Morebath by Eamon Duffy

The Snow Geese by William Fiennes

Ninety Degrees North by Fergus Fleming

Don't Let's Go to the Dogs Tonight by Alexandra Fuller

The Invention of Clouds by Richard Hamblyn

The Scottish Enlightenment by Arthur Herman

Redcoat by Richard Holmes

Churchill by Roy Jenkins

Emergence by Steven Johnson

Peacemakers by Margaret Macmillan

Paris Between Empires 1814-1852 by Philip Mansel

Trieste and the Meaning of Nowhere by Jan Morris

The Intellectual Life of the British Working Classes by Jonathan Rose

Islam's Black Slaves by Ronald Segal

Painted Shadow by Carole Seymour-Jones

Unfinest Hour by Brendan Simms

The Common Thread by John Sulston and Georgina Ferry

God: A Guide for the Perplexed by Keith Ward