The first volume of Margaret Thatcher's authorised biography will be published after her funeral.

The book, which was written by former Daily Telegraph editor Charles Moore and is called Not For Turning, was commissioned in 1997 on the understanding it would not be published during her lifetime.

Its author was allowed full access to Lady Thatcher's private papers and also interviewed her extensively while researching the work.

Lady Thatcher, who did not read the manuscript which ends in November 1982, also supported requests for interviews with her family and people who worked with her and Mr Moore was allowed to see government papers held back from public view under the 30-year rule.

Stuart Proffitt, from publishers Allen Lane, said: "Charles Moore's biography of Margaret Thatcher immediately supersedes all earlier books written about her. Having worked closely with Lady Thatcher on both volumes of her autobiography, and read all the other main books about her, I was astonished at how much Moore says which has never been public before. At the moment when she becomes a historical figure, this book also makes her into a three dimensional one for the first time. It gives unparalleled insight into her early life and formation, especially through her extensive correspondence with her sister, which Moore is the first author to draw on. It recreates brilliantly the atmosphere of British politics as she was making her way, and takes her up to what was arguably the zenith of her power, victory in the Falklands. Moore is clearly an admirer of his subject, but he does not shy away from criticising her or identifying weaknesses and mistakes where he feels it is justified. It is, by any standards, an exceptionally impressive book and to be publishing it at this moment is a rare privilege."

Mr Moore is currently writing the second and final volume called Herself Alone.