This has been known about for some time (Score 1)

While the fact that documents have been released that confirm it's existence and potential design is both new and interesting, the fact that Avro was working on a supersonic disc has been known for a while. I remember hearing it for the first time in a documentary about the history of the Avro in regards to the Avrocar and the Arrow if I recall correctly. Google Project Silverbug and you're likely to see some very similar looking design documents.

A quick Google search spawns this -

http://www.boomslanger.com/images/silverbug03.jpg

http://greyfalcon.us/restored/Project%20Silver%20Bug.htm

While the author has a penchant for Nazi UFOs - a bit of historicity that has since become wild myth - it clearly shows that this was known about for quite a while. Even showing mockups, models, and expected designs. The details of it and how far it came along though, have long since been a matter of debate.

So...... Don't shit on those saying they've seen this before.