There is more to it. She was in remission and kept quiet.
On her claim from 2004 to 2018 she had claimed she struggled to get out of bed or walk without support. She didn't report any change in circumstances during that period.
On her claim form she'd stated: ‘I prefer someone with me at all times when I am outdoors because I have poor balance. There is a risk of falling and dizzy spells.
Her change in health from highly dependent disabled to in remission and able to run alone, is dated as having started around April 2009. She admitted running around four times a week.
It's a substantial change of health circumstances which she failed to notify for nine years, not a minor blip.
Even if she's was entirely telling the truth when she claimed the investigators filmed her during a period when she was fitter, doing three mile runs in under 30 mins, and actually her previous running was much slower and less frequent, she still needed to report to DWP that her lack of balance and inability to walk without support had became an ability to run, alone, at whatever pace, and accept it would impact her claim.
I came close to getting into trouble because I failed to tell DWP how often I was hospitalized, because I saw it as part and parcel of being disabled.
I thought I only had to report it, if it was long enough, or frequently enough for me to not be entitled to PIP and had only reported those. Fortunately they accepted it as a legitimate misunderstanding, gave me a slapped wrist and I now report every admission whether it affects my claim or not.