The Work and Pensions Secretary plunged into ponds, walked the plank and leapt through bales of burning straw for a charity event.
The 60-year-old minister, who introduced the bedroom tax, was among 600 runners who tackled the 10km elite assault course for the fourth annual Swanbourne Endeavour.
Mr Duncan Smith, who lives in Swanbourne, brought a team of 14 civil servants from his department and together they swung on rope swings and crawled through barbed wire.
It took place yesterday because the date falls close to the anniversary of the Battle of Trafalgar on October 21.
Event organiser and Swanbourne estate manager Tom Finchett is still counting funds raised for charity but thinks it will be around £16,000.
He said: “I watched the minster launch himself off ‘walk the plank’.
“He seemed to really enjoy it, I think he’s done all of them since we started and he just gets stuck in.
“It was a really good event, we were lucky with the weather and the there were some really good obstacles this year.
“We had a trench and lots of electric shocks and we pumped the course with lots of water so it was nice and muddy.”
Mr Finchett said he is already looking ahead to next year’s event, which he promises will be bigger and better.
It will once again take place in October and, although a date has not been finalised, there will be some ‘little surprises’.
Money raised from the Swanbourne Endeavour will support four charities – the Royal British Legion, the Soldiers, Sailors, Airmen and Families Association, the Bucks Services Charities and Great Horwood-based Medical Detection Dogs.