Because they were walking across the Bering Strait, they could not take the normal route. Consequently, they didn't have the correct stamps and a landing permit.

It kind of baffles me. I don't think Siberia gets a good press anyway. It brings all sorts of connotations to mind. If they'd just allowed him to carry on with his walk, it would have allowed in a chink of light.

He will be worried that the authorities will not let him walk any further in Russia.

Even when he was crossing deserts, he was thinking about how he was going to do it.