This photograph - taken high up on the North Slope of Alaska on Thursday morning - is special for us. It is a photograph I have always aspired to take. The best pictures can never be retaken.

There were two or three key elements to its capture. Firstly, because the physical enormity of an adult bear is best conveyed head on and from low on the ground, we had to try and find a position where the terrain offered a horizon and an incline between me and the bear. The second and more important dynamic was to use the 25 mph wind to our favour.

Bears can smell us from a long way away so long as they are downwind. Then of course - the overriding factor - was our safety. At all times we had to have an escape route. We knew what to do here and I had the best Inuit guide in the area. I felt safe with him, but please do not try this at home.

This bear is enormous and my positioning shows that off. It was all over in maybe five seconds - but I will never forget them.

People understandably worry about polar bear numbers - but be assured there is a load of big healthy bears on the North Slope. I think we saw over 25 in a week.