It was 30 years after the Romans invaded Britain that they were ready to take on the challenge of conquering the Lake District. With the toughest landscape they had encountered in the country, peopled by a rebellious tribe, it was no small task. Two full legions - 11,000 armed men - marched north, led by two top generals. This extraordinary commitment was rewarded, and within a few years, the whole of Lakeland was under Roman control. Tony Robinson tackles the journey, but, as he discovers on this 50-mile walk from Penrith past Ullswater to Ambleside and on to the Irish Sea at Ravenglass, the Romans encountered beauty and danger in equal measure.