After surpassing Stephen Fry in September, Sarah Brown became the most high-profile Twitter user in the UK.
She has posted almost 1,500 tweets to date, talking about everything from baking cookies and gardening, to charity events and celebrity friends like Naomi Campbell and Paris Hilton.
Since registering with the online service in March, the PM's wife has accumulated over 910,000 followers on her account, SarahBrown10.
She is on track to reach at least a million by the end of the year.
Friend and comedian Kathy Lette explains: “She is a natural communicator.
"It’s just her instinct to communicate good, positive messages about her charitable passions like maternal mortality.”
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