The approach is simple. In the past, each source was judged as a whole. If Bede was an honest reporter of history, then everything he wrote has integrity. If he wrote out of a love for Roman Catholocism, the Germanic peoples, and Northumbria then what he wrote must be seen through those biases. But what if they are both right? And what if each of the sources he used were created by someone with their own degrees of integrity and biases as well? In short, examining and making use of the source materials would be much more complicated and infinitely more difficult than has been imagined.
That is exactly what I discovered in my own research. That is exactly the methodology I employed in studying the nature of the grail, the historicity of Arthur, and the chronology of post-Roman Britain.
At times the approach can be frustrating; there are entire areas which are not covered by any source that can be relied on for certain subjects. Often the materials cannot provide a complete answer, only possibilities. However, what can be used can be relied on. In this period, that’s a welcome change.