The motorcycle racer leaves his comfort zone as he attempts to set a world speed record for a hovercraft. These machines are notoriously difficult to control, so to learn the basic skills needed he's put through his paces by Royal Marines in a military training operation. To achieve his goal, Guy will need to stay over 86mph for a kilometre, but at these speeds, because of the hovercraft's inherent instability, even the most experienced pilots can lose control - and the worsening weather makes things that much more challenging

• Guy Martin