Dame Stella, who has a home near Swaffham, was the first female director general of MI5 and her novels reflect her in-depth knowledge of the security service and how it works.

Dead Line features the author's heroine, Liz Carlyle, a young intelligence officer, in a race against time to stop terrorists disrupting a Middle East peace conference at Gleneagles in Scotland.

The novel is the fourth in the Liz Carlyle series, which started in 2004 with At Risk – set in Norfolk and The Fens.

Bookshop owner Mrs Claire Dunne said Dame Stella, who was director general of MI5 between 1992 and 1996, was kept busy signing copies of Dead Line, and her autobiography and memoirs, Open Secret, for visitors on Saturday.

"People were waiting here for her when she arrived.

"She continued signing her books for nearly two hours and she was very open about herself and chatting with everybody," she said.