The wife of former British prime minister Gordon Brown is to write a memoir which will lift the lid on living in Downing Street, her publisher said Monday. Sarah Brown is to pen the volume, working title 'Behind the Black Door,' which will reveal 'what it's like to shop with (elite police unit) Special Branch' and 'cope with a bad hair day when Carla Bruni's in town,' said publisher Ebury. The ex-premier's spouse Sunday told the million people who follow her on micro- blogging site Twitter the news. 'Just agreed with my publisher Ebury to write a book... so chained to laptop from Monday morning,' she tweeted. The planned publication date for the book is Mother's Day in Britain next year. The 46-year-old moved into Downing Street after marrying Gordon Brown in 2000, when he was finance minister in the Labour government, and the couple brought up their two sons John and Fraser there. Gordon Brown became prime minister and Labour party leader in 2007. After marrying the future prime minister, Sarah Brown quit her job in public relations and became a full-time charity campaigner. A spokeswoman for Sarah Brown said the book would 'reflect on the challenges of moving on from a successful career to forge a new role as an international charity campaigner.' It would also describe her time in Downing Street 'being a devoted mother balancing school plays and state visits; of being married to someone who becomes prime minister,' the spokeswoman added. Sarah Brown campaigned alongside her husband in his unsuccessful bid to remain as prime minister at the head of a Labour government in general elections on May 6. She was credited with bringing out his softer, more human side and received much attention for her use of Twitter, where she built up a huge following. Labour were ousted from power after 13 years at last month's vote. The Conservative party, headed by new Prime Minister David Cameron, formed Britain's first coalition government since World War II with the smaller Liberal Democrat party. 