Royal Baby Watch, Marathon and Prince Harry's Return Have London Abuzz

Duchess Kate is at Kensington Palace, due to give birth any day now.

— -- Mothers know that delivering a baby can sometimes be a marathon and sometimes, if you’re lucky, a sprint.

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The thousands of runners, and their fans, will join an already crowded city full of royal watchers who have been camped out at St. Mary’s Hospital, where Kate is expected to deliver, for days.

“Been here since last Thursday,” one royal superfan, sleeping on a bench outside the hospital, told ABC News.

“We are so close to the due date now,” ABC News royal contributor Victoria Murphy said. “William and Kate are at Kensington Palace, ready to go, just a short drive to the Lindo Wing.”