Step aside Harriet, says Sarah

The biggest surprise of the conference was produced not by Gordon Brown, but by his wife, Sarah.

Just two hours before he was due to deliver the most important speech of his career, the "first lady" of British politics decided she wanted to introduce him personally.

Her arrival on stage – echoing Michelle Obama's endorsement of her husband in last month's Democrat convention – surprised delegates, who had expected that the task would fall to the party's deputy leader, Harriet Harman.

Aides said Mrs Brown only told the Prime Minister over lunch that she would be his warm-up act. The move worked spectacularly as the former public relations executive immediately won over any doubters with a fluent and confident speech.

She told the conference: "I remember the warm welcome you gave me and Gordon at conference after our wedding. I'm so proud that every day I see him motivated to work for the best interests of people all around the country. Sometimes in a world where there is so much to do we don't perhaps have enough time to celebrate what has been done."

To cheers and applause she introduced the Prime Minister to the stage.

He kissed her and told activists: "You can see why I'm proud of Sarah.

"Thank goodness Sarah and I are a team. I'm very proud to be her husband."