A team of historians and scientists is embarking on what is thought to be the first attempt to recreate a pioneering trip through the Grand Canyon. The 280-mile expedition, which will retrace the 1869 passage of US soldier and explorer John Wesley Powell down the Green and Colorado rivers in the American west, is set to start several miles downstream from Glen Canyon Dam in Arizona and is expected to reach Lake Mead by the end of August. Among the nine-strong team is historian and television presenter Dan Snow, geologist Dougal Jerram, ecologist Mike Dilger and maritime historian Sam Willis.