Alan, I should add that I did not actually observe the way(s) the Brit Council went about verifying that my university degree parchment was valid. That was because they gave me a receipt for it before sending it to a room in the same building for authentication. They might very well have undertaken other checks as well as looking for watermarks.

Some years later, I obtained a transcript, supposedly equivalent to my degree parchment, from my university. It had a watermark too! At that time, I recall Guangdong province was no longer accepting university degree transcripts, be they originals or photocopies! Very strange indeed!

I note Taffy, the forum idiot, has posted information about a fake diploma provider. He says they will provide watermarked fakes, but the information he has posted about said provider doesn't say that! That's one reason why he's the forum idiot!