Alastair survived his plunge into icy waters at Battery Rocks in Penzance.
He says: "Once I was numb it was exhilarating. I even went back in for a second dip."
The Guardian is covering the escapade and we'll let you know when video evidence appears online.
Thanks for your well-wishing and tips... The temperature on that day was 4 degrees, by the way!
Photo courtesy of The Guardian