The team - researchers plus a BBC film crew - approached the island in a small plane. The island's surface was judged safe enough to land on - the plane was fitted with skis - and after a bumpy touchdown they ground to a halt, the first expedition of its kind.

Soon the scientists were at work - time was limited with the risk of the weather changing.

They planted a tracking beacon on its surface. This will allow the island's progress to be monitored as currents push it around the Arctic Ocean.

They also carried out a series of measurements using a ground-penetrating radar. They found that the average of thickness of the ice was 42-45m (138-148ft) - the equivalent of the height of a 10-storey building.

For 3,000 years, this colossal block of ice was securely fixed to the coast as part of the Ayles Ice Shelf - but now it is drifting free. Its current location is about 600km (400 miles) from the North Pole, in what is one of the fastest warming regions on Earth.

Although mostly flat, there were places where the ice was cracked or piled high.