Revd Mike Haslam from North Petherton is planning to run 1.72 marathons per day, climbing almost the equivalent of Everest four times during his 16-day sponsored challenge.
Revd Haslam set off on Thursday morning on the 630-mile run along the South West Coastal Path from Minehead to Poole via Land's End.
Father-of-four Mike, 42, Chaplain at Taunton Academy, who will be joined for part of the run by North Petherton friend and 'fellow fool' Steve Bratt.
Revd Haslam said: "It's certainly the biggest challenge I've ever attempted and when Steve and I added up the stats and realised completing the whole length involved climbing a total of 35,000m with an average daily distance of 45 miles, it is fair to say we wondered what we were taking on."
But it is so important to me to step up for those people who have no voice, who are trapped in poverty. We should all have dignity and the chance of a full life. The desperate humanitarian needs of people caught up in conflict in Gaza, Iraq and Syria and the work Christian Aid partners are doing to meet these needs will be uppermost in my mind as I run."
So I will be digging deep and my hope is that as people see us or hear about our crazy run that they will dig into their pockets too and help me reach my target of £3,000."
Revd Mike Haslam: