Epsom & Ewell Harrier Ollie Garrod is no stranger to long-distance races or adding a mix of fun into Parkrun events.

The 33-year-old has completed three marathons, and holds the European record for the fastest 5k dressed as Santa Claus at 16 minutes 51 seconds.

However, this weekend it all changes as Garrod and his old training partner Will Cullen, 27, will be running 100 miles from Richmond to Oxford to raise money for the Alzheimer’s Society.

The duo have so far raised £2,000, and they are due to start at 3pm on Saturday, with the intention of finishing around 11am on Sunday.

“We chose the Alzheimer's Society as funding in dementia is very low despite its massive impact on more than 800,000 people,” Garrod said.

“Dementia is one of the few diseases we could feasibly find a cure for, so research is absolutely crucial.

“The Alzheimer's Society is at the forefront of that research as well as providing support and services so those affected can lead a more connected life, as well as helping out their families.”

He added: “We have seen first-hand some of the impacts of the disease on individuals, and some of the Alzheimer's Society's work.

“They depend on donations so they seemed a great cause for this challenge.”

Garrod’s furthest distance to date is 36 miles, but he is no stranger to the shorter format having won last weekend’s 250th running of the Nonsuch parkrun – his 80th at the venue.

However, he admits this weekend is going to be a completely different story.

“Luckily the route we've chosen is pretty much pancake flat with a total elevation of 55m across the 100 miles and with plenty of scenic spots along the route,” he said.

“The overnight stretch is going to be very hard work both mentally and physically.

“At 2:30am we're due to be running through Reading and the surrounding industrial estates - this will be the ‘tough’ point.”

He added: “Hopefully once the sun comes up we'll be well on our way at around the 70-mile point with just over a marathon left to bash out before Oxford.

“If any well-connected people could make sure we have good weather, that would be great, and I think it's safe to say Monday morning will be pretty painful.”

To sponsor the duo, go to uk.virginmoneygiving.com/WillandOllie100