An accountant who plans to tackle seven marathons in a week next year is running a marathon in Sainsbury's.

Jon O'Shea, 45, a partner at Haslers Chartered Accountants in Loughton, is taking part in a “Treadmill Challenge” in the Loughton superstore today to raise money for Teenage Cancer Trust, St Clare Hospice in Hastingwood and the Haslers Foundation as he prepares for the 2015 extreme charity challenge.

The Essex accountant will attempt seven marathons in seven days on seven continents in January in a bid to raise £50,000 for charity after losing colleagues, chairman Martin Anderson, 57, and Charlotte James, 22, to cancer.

Between 9am and 5.30pm today Mr O'Shea, who has already raised an estimated £2,000 in six hours, plans to run a total of 26 miles on a treadmill with an interval at each mile.

Colleagues from Haslers will alternate in completing a mile each themselves whilst the 45-year-old rests.

Jon said: “The treadmill challenge is a great way of raising cash and awareness for the three charities I am supporting through the World Marathon Challenge.

 “I am proud to be doing this challenge in memory of Martin and Charlotte, raising money for three charities which do fantastic work with people young and old in the local community fighting cancer.

"I have already raised £15,000 which is surprising as I thought we would fundraise the most towards the main event and we still have two months to go.

"It's a hard challenge but well worth it."

He will began his seven marathon challenge on January 17.

You can follow Mr O'Shea's progress or donate to his challenge, here.