woman who thought she had broken a world record after running the London Marathon dressed as a witch was told she would not receive the award because her dress was too short.
Nicola Nuttall completed the 26.2-mile route in April in 3hrs 31mins while wearing a full-length witch's dress and hat, and carrying a broom.
But despite the Trawden Athletic Club runner beating the old time by 29 minutes, the record has not been recognised by adjudicators.
I feel like I've let everybody down. I feel like a failure
Nicola NuttallA spokesman for the Guinness World Records said Miss Nuttall, from Pendle, Lancashire, was not awarded the record because she ran in an altered and "substantially shorter dress" than the one they approved.
The mother-of-two said she was "disappointed" by the decision. "I feel like I've let everybody down. I feel like a failure," she said. "I've been back and forth to them but they have been so strict and inflexible.
"I have had the final response and there is no way they are going to change their minds."
Miss Nuttall explained she initially bought the dress on eBay and sent photographs off to Guinness World Records.
She said she then added two material "side panels" as she was concerned the splits in the skirt would make it too easy for her.
She added: "I was told I had to run it under four hours and I did it in 3hrs 31mins so I've done it in 29 minutes under that time in a dress which had to go right down to my feet, while wearing a witch's hat and carrying a broom all the way round.
Nicola Nuttall completed the 26.2-mile route in April in 3hrs 31mins CREDIT: SWNS.COM
"I got 16 different witness statements from people who were running from all over the country and the application has taken a great deal of time and effort. The only good thing is that I raised £1,700 for the Alzheimer's Society."
A spokesman for Guinness World Records said it had to set guidelines to make it fair.
They said: "With all our records we have a set of guidelines in place beforehand to ensure that everyone who attempts this record has the same requirements to make it fair.
"With costume records, we ask for the applicant to submit a photo beforehand of their costume so it can be approved by records management.
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"Unfortunately, while Nicola's pre-marathon photo met our guidelines of having a floor length dress, her photos from the day show her with a substantially shorter dress with slits cut in for more movement.
"On this basis, the evidence can't be approved as much as we respect and admire Nicola raising money for charity and attempting to set a Guinness World Record in the process."