Kate McCann, whose daughter Madeleine was abducted in Portugal in 2007, says she has not been put off competing in the London marathon by the Boston bombings.
She is an ambassador of the Missing People charity and is aiming to raise £20,000 to mark its 20th anniversary.
"This sickening act is just incomprehensible and the loss of life, especially that of a young child, heart-breaking.
"But I feel strongly that you can't live in fear or you don't have a life."
More top news
The estate agent renting out the property claim there's been lots of interest.
Cold, dry and sunny
Mostly dry and sunny after a frosty start