Anna Harding, 34, has run 8 marathons in her life, but her latest is one for the books.

She ran almost 2,000 back-and-forth laps in her mom's backyard just outside of London to raise money for the World Health Organization’s COVID-19 Solidarity Response Fund.

Harding calculated that if she ran the out-and-back length of the backyard (which is 10.7 meters or 70.2 feet) that she’d be able to complete the marathon in just over 1,971 laps.

Harding said it was the hardest marathon to date because not only was the scenery boring, but also that she had to slow her pace dramatically each time she turned around, which was every ten steps.

It took her just over 6 hours to cross the finish line — which was aptly made from a strip of precious toilet paper — a much slower pace than her personal best which she completed in Amsterdam at just under 4 hours.

Harding said the best part about the marathon was finishing. What kept her going on this epic feat was thinking about all the front line workers who put their lives at risk. She hopes her marathon encourages others to stay home to prevent the spread of COVID-19.

"That message of ‘stay at home’ probably couldn’t be any clearer than stay at home and run in your backyard," Harding told "GMA."