Pen Hadow sets sail for North Pole as Arctic ice melts

British explorer Pen Hadow and his crew have set sail from Alaska, in an attempt to become the first people ever to sail to the North Pole.

With Arctic ice melting at an unprecedented rate, previously inaccessible waters are opening up, creating the potential for their planned 5,500 km (3,500 mile) journey for the first time in human history.