Or Gairdner was still continuing the Victorian approach to a historian's job -- not merely to investigate and observe but to judge, and all against the idea that history has been progressing (slowly and not without bumps) towards the gleaming "here and now", with the 15th century constituting a particularly black and nasty bump in the road. (This was mentioned in the BBC feature, and it really struck a chord with much that I've seen elsewhere, too.)
I had two History teachers when I took my A Level's. One was close to retirement, taught English History and cofidently opined that Disreali was a good Prime Minister but a bad man and Gladstone was the opposite and expected us to write that down. The other taught European Hustiry and told me that history only supplied answers to the questions you asked - change the question and you change the answer - so when reading a history it was important to know what question the historian started with. It was like being on two different planets.