When Claire Squires, 30, began the marathon on Sunday she had raised £500 for the Samaritans, who her mother Cilla had volunteered with for more than 20 years. Today the figure surpassed £1million and more than 68,000 well-wishers had been moved to donate on her JustGiving webpage.
The news came in a tweet via the online fundraising community.
Claire will be be buried next Wendesday alongside her brother, Grant, who died in 2001 aged 25.
Her friend Nicola Short climbed Kilimanjao with Claire two years ago.
She appeared on BBC Breakfast this morning to pay tribute to her friend:
Miss Squires was the 11th participant to die since the event began in 1981.
She collapsed in Birdcage Walk, near St James's Park, on the final stretch of the 26.2-mile course.
She died with the finishing line only one bend away, after 25 miles of the marathon.