European notary is responsible for veryfing authenticity of all documents provided by his clients. And he is liable in case he makes a mistake.
http://www.notaries-of-europe.eu//index.php?pageID=191
https://www.mdpryke-notary.com/2010/03/uk-notaries-public-%E...
In the UK, I believe they are only authorized within the City of London (=/= “London”). But it looks like they can do “international” documents.
The gripping hand here is whether your receiving party will accept an online notarized doc even if you can get it done. Best to confirm that first.